Image forming apparatus with an unapproved copy preventing means

ABSTRACT

An image forming apparatus, such as a copier, includes an unapproved copy preventor mechanism. The image forming apparatus includes a support such as a platen glass for supporting an original document; a light irradiation source for irradiating the original document with a light beam; and a detectors for detecting predetermined wavelength components of a reflected light from the original document which is irradiated with the irradiating light beam. The detector generates detection signals based on the detection of the predetermined wavelength components of the reflected light. An evaluator circuit determines whether the original document is a document which prohibits a production of an unapproved copy based on the detection signals.

BACKGROUND OF THE INVENTION

The present invention relates to an image reproducing apparatus whichreproduces an image by means of electrostatic photography, and moreparticularly relates to an image reproducing apparatus having a meansfor preventing a copying operation to illegally copy a secret documentof an enterprise.

Recently, color image copiers of high-performance have come into wideuse. Therefore, it is anticipated that paper money and securities arefrequently counterfeited using the color image copier. In order toprevent the counterfeiting of paper money and securities, the followingtechnique has been disclosed in Japanese Patent Publication Open toPublic Inspection No. 111977/1980:

When a color document is digitally read out so as to be copied, aspecific pattern on the document is recognized using a signal that hasbeen read out. In the case where the recognized pattern is of papermoney or securities, the copying operation is stopped.

However, in some cases, the aforementioned recognition means forrecognizing the specific pattern makes a mistake.

In order to prevent the occurrence of the mistake described above,Japanese Patent Publication Open to Public Inspection No. 300285/1989discloses the following color copier:

The color copier includes a document scanning means by which a colordocument is subjected to color separation and the color-separated imageis digitally read out. A color separation signal outputted from thedocument scanning means is converted into a density signal, and inaccordance with the density signal, a color image is copied. The colorcopier comprises: a means for recognizing a specific pattern containedin the document, using the color separation signal; and a control meansfor repeatedly conducting the recognizing operation of the recognizingmeans each time the scanning operation is conducted, wherein the controlmeans stops the copying operation when the recognizing means recognizesthe specific pattern on the document. According to the above colorcopier, a plurality of pattern recognizing operations are repeatedlyconducted on the same document to be copied, so that the accuracy ofrecognition can be improved.

According to Japanese Patent Publication Open to Public Inspection No.316783/1989, the following copier is disclosed: The copier comprises: areading means for reading image information from a document; an imageforming means for forming an image on a recording medium in accordancewith the image information that has been read by the reading means; anda judging means for judging that the read document is prohibited frombeing copied, wherein the read image information is subjected toconverting processing in accordance with the result of the judgment.

According to the disclosure of technique explained above, using thesignals of R, G and B inputted from the reading means, documents arediscriminated whether or not they agree with the characteristics ofpaper money or securities that have been previously set. In accordancewith the result of the discrimination, it is finally discriminatedwhether or not they are paper money or securities. In the case where theresult of the discrimination is YES, a conversion parameter is set in aspecific processing circuit so that the document can not be faithfullycopied. In this case, the discrimination is conducted as follows: Withrespect to the inputted signals of R, G and B, a color spectrum of thedocument is compared with the data previously registered in a ROM, oralternatively an image pattern of a portion of the document or theentire document is compared with the pattern data previously registeredin the ROM. Alternatively, the aforementioned two processes may becombined.

The characteristics of a document are extracted by a characteristicextraction circuit, and in accordance with the result of thecharacteristic discrimination, parameter conversion processing iscarried out. With respect to the parameter conversion processing, thefollowing methods are disclosed:

(1) Color conversion conducted according to a parameter of masking andUCR processing

(2) Conversion of magnification, italic characters and mirror images

(3) Edge emphasis, fine line processing, negative and positiveconversion, and character pattern addition.

In order to prevent the counterfeiting of paper money or securities whena document is copied in a printer, the following methods are disclosed:

Video signals are sequentially monitored, and when it is judged that adocument is paper money or securities, the images are subjected to theprocessing of thinning out, fine line, bold line, and screen pattern.

Further, according to Japanese Patent Publication Open to PublicInspection No. 55379/1990, the following method is disclosed:

For example, the pattern of a seal put on paper money or writtencontract, which appropriately expresses the characteristics of aspecific document, is previously stored in the form of templateinformation. When the template information is compared with an imageoutputted after processing, it is judged whether or not it is a case ofcounterfeit. Specifically, the signals of R, G and B sent from the imagereading unit pass through a comparator and AND gate. In the case ofR_(L) <R≦R_(H), G_(L) <G≦G_(H), and B_(L) <B≦B_(H), it is judged thatthe color is a specific one. For example, it is judged that the image isa red seal of paper money.

The digital image signals R, B and G are inputted into thecharacteristic extraction circuit. The characteristic extraction circuittargets a specific pattern and color distribution, and conductscharacteristic extraction processing. According to the result of theprocessing, a portion or an entire drive unit necessary for imageformation is stopped. This technique is disclosed in Japanese PatentPublication Open to Public Inspection No. 210481/1990.

According to another known system a document is provided with a mark bywhich the document can be easily recognized as an original sheet to becopied, or alternatively the document is provided with a second mark.Only when the copier detects the aforementioned mark or the second markon the original sheet to be copied, copying operation is conducted. Whenthe mark is not detected, the original sheet to be copied is notconveyed, or even when the original sheet to be copied is conveyed,image formation is not conducted, and the original sheet to be copied isdischarged from the copier as it is, and a display means displays thatthe original sheet to be copied has been discharged. In this way, thecounterfeiting of paper money and securities can be prevented.

However, according to the above applications for preventingcounterfeiting, it is essentially necessary to provide a technique bywhich a specific pattern can be recognized. Therefore, the constructionis complicated and the cost is increased, which is the first problem.Further, the conventional technique is mainly applied to digitallyoperated copiers.

In the case of a copier including a document scanning means by which acolor document is subjected to color-separation and read out digitally,also including a means for recognizing a specific pattern on thedocument using a color-separation signal outputted from the documentscanning means, the recognizing operation is affected by color ghost, sothat a problem of malfunction is caused.

The phenomenon and cause of-color ghost will be briefly described here.In the color copier, a document image is optically subjected tocolor-separation, so that it is separated to red and blue. Then, the redand blue images are respectively read out. In accordance with a signalsent from an individual image sensor (referred to as CCD hereinafter), acolor of one pixel is determined. Therefore, when the position of CCD ofred and that of blue deviate, a false signal of red or blue is generatedalthough a line is black, which is referred to as color ghost. Thecauses of color ghost will be described as follows:

(1) Color ghost is caused due to pixel deviation between the CCDs causedwhen the accuracy of the mounted CCD is inappropriate, or when the CCDis deformed, or when the CCD deteriorates with age.

(2) Color ghost is caused when the magnification of red and that of blueare different, or when MTF of red and that of blue are different.

(3) Color ghost is caused when the output of red and that of blue aredifferent due to chromatic aberration of a lens.

According to the recognition technique in which color-separation signalssent from the document scanning means are used, the characteristics of aspecific document are made into a pattern so as to be compared.Therefore, a ratio of discrimination for discriminating the specificdocument is low, which is the second problem. In this case, MTF(Modulation Transfer Function) will be explained as follows.

A rate of deterioration of an image can be evaluated when the image iscompared with the original document. However, its evaluation is notquantitative but qualitative. In order to quantitatively evaluate therate of deterioration of an image, MTF used for evaluating a signaltransfer system is adopted.

The modulation transfer function is expressed as follows.

    MTF(%)=(V.sub.max -V.sub.min)/(V.sub.max +V.sub.min)×100

In the above expression, V_(max) is the maximum density level of asubstantial deteriorated waveform in the case where the waveform is readout by the CCD, and V_(min) is the minimum density level of asubstantial deteriorated waveform in the case where the waveform is readout by the CCD. In this case, signal deterioration is explained in thecase where the image is read out by the CCD. In general, the MTFdeteriorates while the image is recorded and reproduced. Deteriorationfactors of the MTF are an optical system, optical traveling system,processing circuit, and recording system. The following directly affectthe deterioration of resolution: the MTF of the lens in the opticalscanning system; the accuracy of a prism surface; the accuracy ofmounting the CCD; the vibration of an optical mirror in the opticaltraveling system; and scanning speed.

Characteristics of the MTF are described as follows.

(1) Compared with the primary scanning direction, the MTF remarkablydeteriorates in the subsidiary scanning direction.

(2) In order to improve the reproduction property of the finest portionof an image, the MTF value must be not less than 30%.

(3) Intensity of MTF correction must be determined in accordance withthe reproduction property of fine lines and the photographic reproducingproperty.

According to the above recognition technique in which thecolor-separation signal sent from the document scanning means is used, aspecific mark for specifying a document is blurred in some cases. Inthis case, it becomes difficult to extract the specific mark.

In the case where there are a large number of specific documents, ittakes a good deal of time for the step of specifying the document andthe step of judging the coincidence of the specific document.Accordingly, the performance of the entire image forming apparatus islowered, which is the third problem.

According to the image reproducing apparatus of the prior art and alsoaccording to the image reproducing apparatus of the present invention,it is possible to prevent a specific document from being copied.However, it is necessary for a specific person to copy the specificdocument for the purpose of providing information. In other words,information must be provided to the specific person. On the other hand,information must be kept secret from other persons. Specifically, thespecific document is permitted to be copied by the first generation, andprohibited from being copied by the second and after generations.

SUMMARY OF THE INVENTION

The first object of the present invention is to provide an imagereproducing apparatus in which a specific document can be securelyprevented from being illegally copied, by using a simple and inexpensivemeans, wherein the means is capable of being applied to both digital andanalog machines.

The second object of the present invention is to provide an imagereproducing apparatus in which a specific document can be securelyprevented from being illegally copied, by using a simple and inexpensivemeans.

The third object of the present invention is to provide an imagereproducing apparatus in which the copying capability is not loweredeven after a large number of specific documents have been registered,and the specific documents can be positively prevented from being copiedeven when the specific marks are blurred.

The fourth object of the present invention is to provide an imagereproducing apparatus in which a specific document is permitted to becopied by the first generation, however, the specific document isprohibited from being copied by the second and after generations.

In order to accomplish the first object, the present invention is toprovide an image reproducing apparatus in which a latent image is formedon an image forming body by a beam of light reflected from a documentand the formed image is reproduced, the image reproducing apparatuscomprising a control unit for discriminating the coincidence of aspecific document by an electric signal outputted from a color detectingunit to detect a wavelength component of the beam of light reflected onthe document.

The color detecting unit detects the under color of a document.

The color detecting unit is operated in a period of time until anexposure light source is stabilized.

The control unit continues processing while the result of discriminationor the motion of discrimination is made to be invalid.

In order to accomplish the second object, the present invention is toprovide an image reproducing apparatus having an image reading means bywhich an image of a document stacked on a platen is color-separated anddigitally read out, wherein color-separation is conducted by a digitalsignal outputted from the image reading means so that the color isseparated to a recording color. In this image reproducing apparatus, aspecific color region is provided in a color separation table by which acolor is separated from the digital signal obtained by the image readingmeans in a preliminary scanning.

The present invention is to provide an image reproducing apparatus,wherein a setting means is provided, by which the specific color regionis changed or added.

The present invention is to provide an image reproducing apparatus,wherein the setting means optically scans a specific document or aspecific color coated on the specific document.

The setting means employs at least one of the control key, ID card andcode number.

Color information exceeding the frequency corresponding to color ghostis used as effective data, wherein the color information is the digitalimage data in the sampling data obtained by preliminary scanning in aregion except for the black region.

In the color separation table corresponding to the color informationadopted for the effective data, a specific color region is set beingextended at least in the setting time.

In order to accomplish the third object, the present invention is toprovide an image reproducing apparatus having an image reading means bywhich an image of a document stacked on a platen is color-separated anddigitally read out. The image reproducing apparatus comprises: aspecific mark storage means for storing specific color region datacorresponding to a specific mark color attached onto a specific documentand also storing specific frequency data showing the number of dotscomposing a specific mark attached onto the specific document; acounting means for counting the number of sampling dots composingdigital image data in the specific color region, wherein the digitalimage data is sampled in the preliminary scanning conducted previouslyto the image formation process; and a comparing means for comparing thecounting data provided by the counting means with the specific frequencydata.

The counting means counts the number of sampling dots of the specificmark except for an outer frame.

The counting means counts the number of sampling dots of the specificmark including an outer frame.

The image reproducing apparatus of the invention comprises: a blurredimage detection means for detecting that the outer frame of the specificmark is blurred; and a discontinued image compensation means forcompensating at least one of the primary scanning and the subsidiaryscanning in accordance with the output of the blurred image detectionmeans.

In order to accomplish the fourth object, the present invention is toprovide an image reproducing apparatus having an image reading means bywhich an image of a document stacked on a platen is color-separated anddigitally read out so that an image of a plurality of colors isreproduced in a plurality of image forming sections. The imagereproducing apparatus comprises: a first judging means for outputting anoutput signal by which coincidence with a specific document is judged; asecond judging means for judging a reproduced color; a warning andprohibiting means for warning and prohibiting an image forming motion inaccordance with an output signal sent from the second judging means; anda releasing means for releasing the warning and the prohibition of theimage forming motion, wherein the image forming operation is carried outwhile an image of a color except for black is added in accordance withan output signal sent from the releasing means, a coincidence signalsent from the first judging means, and a non-coincidence signal sentfrom the second judging means.

The first and second judging means are composed of a color separationtable.

The color reproducing apparatus of the invention includes a memory whichstores characters composing the specific mark attached onto the specificdocument, wherein the characters are stored in a half tone dot manner.

The color separation table will be explained here.

FIG. 6 is a conceptional view showing a color separation map employed inthe image reproducing apparatus for accomplishing the first object ofthe present invention.

In this case, a color separation map for separating colors into red,blue and black will be explained here.

The color separation map is composed in the following manner:

Light reflected on the surface of a document is subjected tospectrography at the wavelength of about 540 nm. A coordinate surface ofV_(r) and V_(c) is composed of a light intensity of a cyan componenthaving a long wavelength region, and a light intensity of a redcomponent having a short wavelength region. In the coordinate surface ofV_(r) and V_(c), the colors of red, blue and black of the recordinglight are made to correspond with the density levels. In this case, onthe coordinate surface V_(r), V_(c), the origin represents that thedensity is maximum. Accordingly, it should be noted that the density ofa point is lowered when the point is separated from the origin.According to this color separation map, colors can be separated intothree groups of red, blue and black not including the colors of greenand purple. In this case, a sufficient boundary is provided between redand black for color separation, however, a sufficient boundary is notprovided between black and blue for color separation. The map boundaryis set, giving consideration to the compensation capability of colorghost described later.

FIG. 10 is a conceptional view showing a map employed in the imagereproducing apparatus for accomplishing the second and third objects ofthe present invention.

On the color separation map shown in FIG. 10, a specific color region isprovided, in which reflected light sent from the background of aspecific document or the specific mark expressing the specific documentis projected on the surface of the coordinate V_(r), V_(c). In FIG. 10,the reflected light is projected on the hatched region located in thered region. The reason why this region is selected is that a sufficientboundary is provided between red and black while consideration is givento the color ghost compensation capability. Other points are the same asthose of the color separation map shown in FIG. 6. Therefore,explanations are omitted here.

FIG. 13 is a conceptional view showing a map employed in the imagereproducing apparatus for accomplishing the third and fourth objects ofthe present invention.

On the color separation map shown in FIG. 10, a specific color region isprovided, in which reflected light sent from the background of aspecific document or the specific mark is projected onto the coordinatesurface V_(r), V_(c) so that the first specific color region is formed,and further light reflected on the document background is projected onthe coordinate surface V_(r), V_(c) so that the second specific colorregion is formed. In the second specific color region, the reproductioncolor is determined by the color code and density data. In this case,the first specific color region and the second specific color region arein the same red region, and only the density of the first specific colorregion and that of the second specific color region are different.However, the present invention is not limited to the specific pattern,and the specific color regions may be provided in different colorregions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration showing the overall arrangement of anexample of the image forming apparatus in which an analog system is usedto accomplish the first object of the present invention.

FIG. 2 is a plan view showing the optical scanning system of the imagereproducing apparatus in which the analog system is applied.

FIG. 3 is a graph showing an output current outputted from the opticalsensor when a document is scanned by one scanning operation.

FIG. 4 is a graph showing an output current outputted from theconventional optical sensor when a document is scanned by one scanningoperation.

FIG. 5 is a block diagram showing the essential construction of thedigital image reproducing apparatus to accomplish the first object ofthe present invention.

FIG. 6 is a conceptional view of the color separation map employed inthe image reproducing apparatus to accomplish the first object of thepresent invention.

FIG. 7 is a view showing a model of the scanning range in thepre-scanning operation of the image reading section AA of the presentinvention.

FIG. 8 is a graph showing the frequency distribution of a typicaldensity level obtained in the pre-scanning.

FIG. 9 is a block diagram showing the essential construction of theimage reproducing apparatus to accomplish the second object of thepresent invention.

FIG. 10 is a conceptional view of the color separation map employed inthe image reproducing apparatus to accomplish the second and thirdobjects of the present invention.

FIG. 11 is a block diagram showing an outline of the construction of theimage processing section of an example of the image reproducingapparatus to accomplish the third object of the present invention.

FIG. 12 is a block diagram showing an outline of the construction of thesignal extraction circuit.

FIG. 13 is a conceptional view of the color separation map employed inthe image reproducing apparatus to accomplish the third and fourthobjects of the present invention.

FIG. 14 is a block diagram showing the essential construction of anexample of the image reproducing apparatus to accomplish the fourthobject of the present invention.

FIG. 15 is a sectional view showing an outline of the construction ofthe image reproducing apparatus in which a digital system, which iscalled a "Konica New Color" is employed.

FIG. 16 is an illustration showing an embodiment of indicationcharacters indicating the second generation of the specific document.

FIG. 17(A) and 17(B) are illustrations showing an embodiment ofdiscrimination method to discriminate between the first generationdocument and the second generation copy of the first generation documentby means of a specific mark.

FIG. 18 is a conceptional view of the color separation map employed inan embodiment of discrimination method to discriminate between the firstgeneration document and the second generation copy of the firstgeneration document, only by means of background color of a specificdocument.

DETAILED DESCRIPTION OF THE INVENTION

An example of the image reproducing apparatus to accomplish the firstobject of the present invention will be explained with reference to theaccompanying drawings.

FIG. 1 is an overall arrangement view of the image reproducing apparatusto accomplish the first object of the present invention. That is, FIG. 1is a schematic illustration showing an outline of the construction of anexample to which the analog system is applied. FIG. 2 is a plan viewshowing the optical scanning system of the image reproducing apparatusin which the analog system is applied.

As illustrated in FIG. 1, the image reproducing apparatus 100 comprises:a platen 1 made of platen glass (referred to as platen glass PG in thisexample hereinafter); a light source 2 for illuminating a document OGplaced on the platen 1 with a beam of white light; a first mirror 3mounted on a moving member M1 having the light source 2, wherein thefirst mirror 3 reflects a beam of light sent from the document OG; a Vmirror unit M2 including a second mirror 4 and third mirror 5 whichreflect the beam of light sent from the first mirror 3; an imageformation lens 6 through which an image is formed on an image formingbody 20 by the beam of light sent from the V mirror unit M2; and afourth mirror 7 which reflects the beam of light sent from the imageformation lens 6 to the image forming body 20. The image reproducingapparatus 100 further comprises: an analog type optical documentscanning system A in which a beam of light reflected on the document isilluminated on the image forming body 20; an image formation processingsection B for carrying out the electrostatic photographing process onthe image forming body 20, the image formation processing section Bincluding a scorotron charger 21, developing unit 22, transfer unit 23,separation unit 24, and cleaning unit 25; and a sheet supply system Cfor supplying recording sheets P to the transfer and separation section.When the electrostatic photographing processing is carried out, adocument image can be formed on the recording sheet P which is formed,for example, of a single material such as paper. The image reproducingapparatus further comprises a function for discriminating thecoincidence with a specific document by an output signal sent from acolor detecting section for detecting the wavelength component of a beamof light reflected on the background of the document OG.

In this example, the specific document is defined as an informationtransmitting medium such as a document and a drawing relating to thesecret of an enterprise, wherein the specific document is stipulated inthe illegal competition preventing law. For example, the confidentialdocuments are controlled in an enterprise while a seal of "Confidential"is attached onto the documents. Color of the background of theconfidential documents is red or blue, so that only specific persons canapproach the confidential documents.

As illustrated in FIG. 2, the optical document scanning system Aincludes a color detecting section mounted on a member M3. In this case,the color detecting section is composed of a color filter F provided inan optical path between the third mirror 5 and the image formation lens6, and only specific wavelength components can be transmitted throughthe color filter F, and also the color detecting section is composed ofan image formation lens L for forming an image using a beam of lighttransmitted through the color filter F, and an optical sensor PHgenerating a current in accordance with the light intensity. The opticaldocument scanning system A constructed in the manner described aboveforms an image on the optical sensor PH using integrated light sent froma rectangular region on the document surface. Accordingly, when theimage formation lens L (shown in FIG. 2) is adjusted, a region fromwhich light is collected can be arbitrarily specified. The color filterF is characterized in that only the wavelength component reflected inaccordance with the background color of the document OG can betransmitted through the filter F. Consequently, only when the wavelengthcomponent of light reflected on the background of the document is in aspecific region, the light can be transmitted through the color filter Fand received by the optical sensor PH, so that a current can beoutputted in accordance with the light intensity. In other words, theoptical sensor PH outputs a current in accordance with the lightintensity of the wavelength component which is the same as thebackground color of the specific document.

The optical sensor PH is connected with a control section 30 through anamplifier AMP. Due to the foregoing, an output signal of the opticalsensor PH is amplified to a signal level so that the signal can beprocessed by the control section 30. In the control section 30, acomparison is made between the level of the output signal sent from theoptical sensor PH, and the signal level corresponding to density.According to the result of the comparison, it is discriminated whetheror not the level of the output signal coincides with the density of thebackground of the specific document.

When an operation panel 10 is operated, the control section 30 controlsthe optical document scanning system A, image formation processingsection B, and sheet supply system C, so that the image formingprocessing can be carried out.

FIG. 3 is a graph showing an output current outputted from the opticalsensor when a document is scanned by one scanning operation. Asexplained above, only the wavelength component corresponding to thebackground color of the specific document is transmitted through thecolor filter F. As shown in FIG. 3, a high level current is outputted atthe first and second halves, which shows it is a non-image region inwhich an image such as characters does not exist. A region locatedbetween the first and second halves corresponds to the image region inwhich characters are written. Since black ink is used in the imageregion, light of all wavelength is absorbed, and the light collected tothe optical sensor PH corresponds to the photographic density of therectangular region. Therefore, the level of the output signal of theregion in which characters are included is low compared with the levelof the signal of the non-image region. In any cases, light of thewavelength component reflected by the background color of the specificdocument is detected.

With reference to FIGS. 1 to 4, the operation of the image reproducingapparatus of this example will be explained as follows.

An operator opens the platen cover PK, and sets a document OG on theplaten glass PG. Then the operator sets the number of copies on theoperation panel 10, and presses a copy switch. As illustrated in FIGS. 1and 2, the control section 30 turns on the light source 2, and a beam ofwhite light is illuminated on the document OG in such a manner that theilluminated portion is formed rectangular. In this way, scanning isconducted at a predetermined speed. By the control of the controlsection 30, the V mirror section M2 is moved in the same direction asthat of the light source 2 at half speed. Due to the foregoing, a beamof reflected light sent from the document OG is received by the lightsensor PH through the first, second and third mirrors 3, 4, 5. This isthe pre-scanning operation conducted before the image forming operation.In general, in the analog type image reproducing apparatus, thepre-scanning operation is previously carried out for the purpose ofautomatically adjusting the copy density in accordance with the densityof documents. In the pre-scanning operation, EE-processing is conducted,by which an appropriate density compensation patten, which is called agamma table, is selected in accordance with a document densityhistogram, and also APS-processing is conducted, by which the documentsize is detected when the number of yellow bands of the platen cover iscounted.

In the pre-scanning operation of this example, in addition to the EE andAPS processing described above, the discrimination processing is alsocarried out, by which a discrimination is made between the document OGplaced on the platen glass PG and the specific document, that is, it isdiscriminated whether or not the document OG coincides with the specificdocument.

Since the color filter F is provided, through which only wavelengthcomponent of light reflected by the background color of the specificdocument is transmitted, when a current is outputted from the opticalsensor PH in the pre-scanning operation as shown in FIG. 3, it ispossible to detect that the document OG placed on the platen glass PGcoincides with the specific document when the output current of theoptical sensor PH is detected by the control section 30. In the casewhere the document OG placed on the platen glass PG coincides with thespecific document, a sign, such as "Confidential", "Unapproved Copy","Enterprise Confidential", or "Business Confidential", is displayed onthe control panel, and the image forming processing is not carried out.As described above, in the image reproducing apparatus of this example,whether or not the document placed on the platen glass coincides withthe specific document is judged by the color. Therefore, it is notnecessary to use a complicated pattern recognizing circuit forpreventing the illegal copying operation. Since the background color ofthe document is detected, the specific document can be discriminatedapproximately perfectly.

In the case where the color filter F is provided in the optical documentscanning system A, through which only wavelength component of lightreflected by the background color of the specific document istransmitted, the specific document may be discriminated not only in thepre-scanning operation but also in the image forming process.

In the example, the color filter F has the spectral characteristics inwhich the wavelength component of a beam of light reflected by thebackground color of the specific document can be transmitted through thefilter F. However, the present invention is not limited to the specificembodiment. Of course, a color filter may be employed, through which thewavelength component of a beam of light reflected by the color of themark attached to the specific document can be transmitted.

In the case where the color filter F is not provided in the opticaldocument scanning system A, through which only wavelength component oflight reflected by the background color of the specific document istransmitted, the same discrimination processing can be carried out.

FIG. 4 is a graph showing an output current outputted from theconventional optical sensor when a document is scanned by one scanningoperation. In the graph, is shown a density distribution in thewavelength region peculiar to the optical sensor. The graph shows thatthe output level can be classified into three stages. The maximum levelregions formed at both ends of the graph show the level of the outputcurrent corresponding to light reflected on the platen cover PG. It isshown that there is no document at both ends of this graph. The regionof the medium level shows the level of the output current correspondingto light reflected by the non-image region of the document. The regionof the low level shows the level of the output current corresponding tolight reflected by the image region of the document. Consequently, whenthe data of the medium level is previously provided, the specificdocument can be specified from the background color even if the colorfilter F is not used.

When the pre-scanning operation is carried out in the beginning afterthe light source 2 has been turned on, the same discriminationprocessing can be carried out even if the color filter F, through whichthe wavelength component of light reflected by the background color ofthe specific document can be transmitted, is not provided in the opticaldocument scanning system A. Specifically, unless a predetermined periodof time, for example, one second has passed after the light source 2 wasturned on, the output of the light source 2 can not be stabilized. Whilethe output of the light source 2 is not stabilized, the intensity oflight emitting energy is low, and the wavelength of emitted lightdeviates to a specific region, for example, the wavelength of emittedlight deviates to a wavelength region corresponding to red. When adocument is scanned with the light source 2 at this time, the wavelengthof light reflected by the regions corresponding to red and white is thesame as the wavelength of red. In this case, even when a color filter isnot used, the background color of a specific document can be detected.When the pre-scanning operation is carried out in this period of time,the capacity of the image reproducing apparatus can be improved, forexample, the throughput (the number of copies per one minute) can beincreased.

Next, an example of the digital type image reproducing apparatus foraccomplishing the first object of the present invention will beexplained as follows.

FIG. 15 is a sectional view showing an outline of the construction ofthe digital type image reproducing apparatus to which KNC (Konica NewColor) process is applied.

As illustrated in FIG. 15, the image reproducing apparatus 200comprises: a platen 201 made of platen glass (referred to as platenglass PG in this example hereinafter); a light source 202 forilluminating a document OG placed on the platen 201 with a beam of whitelight; a first mirror 203 mounted on a moving member M1 having the lightsource 202, wherein the first mirror 203 reflects a beam of light sentfrom the document OG; a V mirror unit M22 including a second mirror 204and third mirror 205 which reflect the beam of light sent from the firstmirror 203; and an image formation lens 206 through which an image isformed on a line sensor LS1 for red and a line sensor LS2 for cyanthrough a dichroic mirror (shown by DM in FIG. 5). These units composean image reading section AA. The image reproducing apparatus 200 alsocomprises: an image processing section BB in which a digital imagesignal sent from the image reading section AA is converted into a colorsignal corresponding to a recording color; a writing section CC whichemits a laser beam in accordance with a recording signal and conductsscanning on the image forming body 220 for each dot; an image formationprocessing section DD including a scorotron charger 221, developingunits 222Y, 222M, 222C, 222BK, transfer unit 2223, separating unit 2224,and cleaning unit 225, wherein electrostatic photographic processing iscarried out in the image formation processing section DD; and a sheetfeeding system EE which feeds recording sheets P to the transfer andseparation sections. When the electrostatic photographing processing iscarried out in the above apparatus, a color image of the document isreproduced on the recording sheet P. The digital type image reproducingapparatus described in this specification will be explained inaccordance with the above construction.

The image reproducing apparatus 200 of this example is further providedwith a function in which the coincidence with a specific document isdiscriminated by an output signal sent from the color detecting sectionfor detecting the wavelength component of light reflected by thebackground of the document OG.

FIG. 5 is a block diagram showing the essential construction of thedigital image reproducing apparatus to accomplish the first object ofthe present invention.

In FIG. 5, the document OG is placed on the platen glass PG. Lightreflected by the document OG is projected to the dichroic mirror DMcomposing the optical image reading system AA shown in FIG. 15. Then thelight is subjected to spectral processing by the dichroic mirror so asto be separated to red and cyan images. After that, the images arerespectively formed on the line sensors LS1 and LS2. In this case, thecutoff wave length of the dichroic mirror DM is about 540 nm. Due to theforegoing, the red component is transmitted and the cyan component isreflected. The line sensors LS1 and LS2 respectively output currentsI_(R) and I_(C) in accordance with the light intensity. These linesensors LS1 and LS2 are included in the image reading section AA. Thesecurrents I_(R) and I_(C) are subjected to shading-compensation by theA/D converters AD1 and AD2. At the same time, these currents I_(R) andI_(C) are A/D-converted into digital image signals V_(r) and V_(c) of 6bits, and sent to the color separation table 231. The digital signalV_(r) shows a density level of the red component, and the digital signalV_(c) shows a density level of the cyan component of the document image.

A high speed ROM is used for the color separation table 231, andpredetermined data is previously written in the color separation table231 as shown in FIG. 6. Specifically, 8 bit data is written in the colorseparation table, wherein the 8 bit data relates to the recording colorcorresponding to the 6 bit digital image signal V_(r) showing thedensity level of the red component, and also corresponding to the 6 bitdigital image signal V_(c) showing the density level of the cyancomponent. In this case, the data relating to the recording colorcomposing the color separation table 231 is, for example, the 2 bitcolor code data for designating the color of developer, and the 6 bitdensity data for determining the density of the recording color.Consequently, the color separation table 231 outputs the data relatingto the recording color in the form of a color signal.

The color codes are determined by the specification. For example, thecolor codes are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                Color Code                                                            ______________________________________                                                Black 00                                                                      Blue  01                                                                      Red   10                                                                      White 11                                                              ______________________________________                                    

The density data is expressed as follows.

    [Density data]=(V.sub.r +V.sub.c)/2

As expressed above, the density data is obtained when the density levelof the cyan component and that of the red component are averaged. Inthis example, this density data is not used, so that it is not soimportant.

Since the color separation table 231 is constructed in the mannerdescribed above, a color signal of 8 bits can be outputted, wherein thecolor signal is composed of color code and density data of the recordingcolor corresponding to the digital image signals V_(r) and V_(c).

In this example, the image processing section BB composed of the A/Dconverters AD1, AD2 and the color separation table 231. In this case,the color separation table 231 corresponds to the color detectingsection.

The control section 230 discriminates whether or not the color code datacomposing the color signal coincides with the color code datacorresponding to the background color of a specific document.Specifically, the color separation table 231 is exclusively used forpre-scanning, and a color separation table exclusively used for imageformation processing is separately provided, which will not be explainedin detail here.

In accordance with the inputted signal sent from the operation panel 10,the control section 230 controls the image reading section AA, imageprocessing section BB, writing section CC, image formation processingsection DD, and sheet supply section EE, so that image formationprocessing can be carried out. In this connection, the control section230 carries out the ACS processing, EE processing, and APS processing,and each processing will be explained below. By the ACS processing, thecolor codes of red, blue and black are counted through pre-scanning sothat the document color is judged. By EE processing, an appropriatedensity compensation patten, which is called a gamma table, is selectedin accordance with a document density histogram. By the APS processing,the document size is detected when the number of yellow bands of theplaten cover is counted. The detail of the processing will not beexplained here since it is not related to the present invention .

In this case, the operation of the image reading section AA inpre-scanning will be briefly explained here, and also the densitydistribution on a typical document will be briefly explained here.

FIG. 7 is a view showing a model of the scanning range in thepre-scanning operation of the image reading section AA of the presentinvention.

As shown in FIG. 7, a sampling range used for discrimination processingis 100 mm long in the primary scanning direction, and 162 mm long in thesubsidiary scanning direction. For example, sampling of data isconducted for each 1 mm in the primary scanning direction and for each0.25 mm in the subsidiary direction. Therefore, about 64800 points ofsampling data can be provided.

FIG. 8 is a graph showing the typical frequency distribution of densitylevel obtained through pre-scanning.

In FIG. 8, in general, the density level of the background of a documentis expressed by the maximum frequency P_(max), and the density level ofcharacters is expressed by the second maximum frequency 1/2P_(max).

With reference to FIGS. 5 to 8 and FIG. 15, the pre-scanning processingoperation of the image reproducing apparatus 200 of this example will bedescribed as follows.

First, the operator opens the platen cover and puts the document OG onthe platen glass PG. Then the operator sets the number of copies usingthe operation panel 210, and presses the copy switch. As illustrated inFIG. 15, the control section 230 turns on the light source 202. Then thelight source 202 is moved at a predetermined speed while the lightsource 202 illuminates the surface of the document 0G with white light,the illuminated portion being formed rectangular. The control section230 moves the V mirror section M22 at half the speed of the light source202 in the same direction as that of the light source 202. Due to theforegoing, the document OG is scanned. A beam of light reflected on thesurface of the document OG is reflected by the first, second and thirdmirrors 203, 204, 205. Then the beam of light is divided into a red anda cyan component by the action of the dichroic mirror DM. Then a redimage is formed on the red line sensor LS1 by the image formation lens206, and a cyan image is formed on the cyan line sensor LS2. Thescanning conducted by the image reading section AA is the pre-scanningconducted before the image formation process. Electric currents I_(R)and I_(C) outputted from the red and cyan line sensors LS1 and LS2 inthe pre-scanning, are respectively subjected to shading compensation bythe A/D converters AD1 and AD2. At the same time, the currents aresubjected to the A/D conversion, so that the currents are converted intothe digital image signals V_(r) and V_(C) of 6 bits, and then the imagesignals are sent to the color separation table 231. The color separationtable 231 sends a color signal of 8 bits corresponding to the digitalimage signal to the control section 230.

The control section 230 makes a comparison between the color code dataof 2 bits composing a color signal and the predetermined datacorresponding to the background color of the specific document, and adiscrimination is made to judge whether the color code data coincideswith the predetermined data. In this way, it is discriminated whether ornot the document OG put on the platen glass PG is the specific document.As a result of the forgoing, the control section 230 displays the sign,such as "Confidential", "Unapproved Copy", "Enterprise Confidential" or"Business Confidential" on the display provided on the control panel,and the image formation process is not carried out. As described above,the image reproducing apparatus of this example discriminates thespecific document by the color, so that a complicated patterndiscrimination circuit is not required to prevent an illegal copyingoperation. Since the background color is detected, the specific documentcan be perfectly discriminated.

Output of the light source 202 is not stabilized unless a predeterminedperiod of time, for example, one second passes after the power sourcewas turned on. In the period of time in which the output of the lightsource 202 is not stabilized, the light emitting energy is so low thatthe wavelength of emitted light deviates to a specific wavelengthregion, for example, the wavelength of emitted light deviates to awavelength region of red. When the document OG is scanned by the lightsource 202 in this period of time, the wavelength of light reflectedfrom a red and a white region is the same as the wavelengthcorresponding to red. In the case where the background color of thespecific document is red, it is possible to detect the reflected light.Accordingly, when the pre-scanning operation is carried out in thisperiod of time, the performance of the image reproducing apparatus canbe improved, for example, the throughput can be enhanced.

According to the above two examples, the color detecting means detectsthe wavelength component of light reflected on the surface of thedocument OG, and an electric signal is outputted from the colordetecting means. By this electric signal, the control section 230discriminates whether or not the document OG placed on the platen glassPG coincides with the specific document. In this way, the specificdocument is discriminated by its color. Accordingly, a complicatedpattern discriminating circuit is not required. Further, the imagereproducing apparatus can be applied to both the digital and analogmachines. When the background color of the document is detected, thespecific document can be approximately perfectly discriminated.

Next, an example of the image .reproducing apparatus to accomplish thesecond object of the present invention will be explained as follows.

The image reproducing apparatus to accomplish the second object of thepresent invention is applied to the digital system. The digital imagereproducing apparatus 200 to which what is called KNC process isapplied, was already explained with reference to FIG. 15. Since thepre-scanning operation of the image reading section AA and the densitydistribution on a standard document were briefly explained before, theexplanation will be omitted here.

FIG. 9 is a block diagram showing the primary portion of an example ofthe image reproducing apparatus to accomplish the second object of thepresent invention.

The image reading section AA was already explained with reference toFIGS. 5 and 15, so that the detailed explanation will be omitted here.The document OG is placed on the platen glass PG. The cutoff wavelengthof the dichroic mirror DM is about 540 nm. Due to the foregoing, a redcomponent is transmitted and a cyan component is reflected. The linesensers LS1 and LS2 outputs the currents I_(R) and I_(C) in accordancewith the intensity of received light, wherein the currents are outputtedby the unit of a pixel.

In this example, the following new construction is provided. The imageprocessing section BB includes a color ghost detecting means 234 andsetting means 232. Further, a distribution means S is provided forconnecting the color ghost detecting means 234 with the color separationtable 231A and the control section 230.

For the color separation table 231A, a high speed ROM is used. In thecolor separation table 231A, the predetermined data shown in the colorseparation map illustrated in FIG. 10 is written in. The digital imagesignal V_(r) of 6 bits shows the density level of a red component, andthe digital image signal V_(c) of 6 bits shows the density level of acyan component. Specifically, the color signal data of 8 bits of therecording colors corresponding to the digital image signals V_(r) andV_(c) is written in the color separation table. In this case, the colorsignal data relating to the recording colors composing the colorseparation table, includes the color code data of 2 bits for designatingthe color of developer, the specific color code data of 1 bit forshowing the specific color, and the density data of 5 bits fordetermining the density of the recording color. Consequently, the colorseparation table 231 outputs the data relating to the recording color inthe form of a color signal. Concerning the color signal, as comparedwith the digital image signals V_(r) and V_(c), the gradation level ofthe density signal is lowered. The reason is that the density region ofthe low density level is cut off because the frequency of the color oflow density level is experientially low.

Specifically, the color separation table 231A is exclusively used forpre-scanning. In this example, a color separation table exclusively usedfor image forming process is separately provided. The detailedexplanation of the color separation table will be omitted here.

The specific code data is defined as the code data that shows thewavelength of light reflected by the background color of the specificdocument or reflected by the color of a mark attached onto the specificdocument. In this example, the bit of the code data corresponds to theLMB of the color code data.

The color code is determined by the specification. For example, thecolor code is shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                         Color Code                                                   Color            Specific Code                                                ______________________________________                                        Black            0     00                                                     Blue             0     01                                                     Red              0     10                                                     Red              1     10                                                     White            0     11                                                     ______________________________________                                    

According to the-color separation map shown in FIG. 10, the specificregion, corresponding "1" of the specific code data, is provided in thered region. Therefore, the color code is "110". However, the presentinvention is not limited to the above embodiment, and the specificregion may be provided in either of the regions in the color separationmap shown in FIG. 10, and further a plurality of regions may be set bythe setting means 232 described later.

The density data can be expressed by the following expression.

    (Density data)=(V.sub.r +V.sub.c)/2

As expressed by the above expression, the density data is found when thedensity level of the cyan component and that of the red component areaveraged.

When the color separation table 231A is constructed in the mannerdescribed above, a color signal of 8 bits can be outputted which iscomposed of color code data and density data corresponding to therecording color determined by the digital image signals V_(r) and V_(c).

By the setting means 232, a change or addition of the specific region inthe color separation map shown in FIG. 10 can be set in the colorseparation table 231A. Specifically, when LMB in the color code datawritten in the ROM is rewritten by the ten keys disposed on theoperation panel, the specific color region can be changed or added.

Unless at least one of the control key, ID card and code number is used,this setting operation can not be conducted. In this case, the controlkey is defined as a key for permitting the peculiar adjusting conditionto be set on the image reproducing apparatus 200, and the ID card or thecode number is used for discriminating a person or a section in theoffice to use the image reproducing apparatus, and the setting conditionof the image reproducing apparatus 200 can be changed by the ID card orthe code number. When the ID card or the code number is used togetherwith the control key, the specific document can be prevented from beingillegally copied.

Further, the specific color region expressing the background color ofthe specific document may be determined when the document OG placed onthe platen glass PG is read and scanned. In the setting of the specificcolor region, a value obtained by the actual scanning operation is of abackground color of a sheet of specific document; therefore, the colorregion obtained by the value expresses only a point in the colorseparation map. Therefore, even a small fluctuation of the backgroundcolor of the specific document can not be allowed. For this reason, itis actually necessary to provide an allowance to the region when thespecific color region is determined. Therefore, in this embodiment, thespecific color region is determined in such a manner that the backgroundcolor read from the specific document is enhanced according to anallowable range which is an experimental value.

The distribution means S distributes the color signal of 8 bits sent outfrom the color separation table 231A to the color ghost detecting means234 and control section 230.

The color ghost detecting means 234 detects a slender color zone at theedge of a black image, and also detects a slender color zone where thecolor is changed. In this case, the slender color zone is detected asghost. For example, the detection is conducted by a color patternmethod, which will be described as follows:

When 7 pixels including the target pixel coincide with the previouslystored color pattern, the target pixel is determined to be ghost.Specifically, the color ghost detecting means 234 is a color ghost tablewritten on the high speed ROM. In this case, the color ghost tableincludes: a color pattern that is a row of color code data correspondingto the 7 pixels containing the target pixel and peripheral pixels; andghost data that is the code data showing whether or not the target pixelis color ghost. In this case, the color ghost detecting means 234 isoperated in the following manner. The color code signal sent out fromthe color separation means 235 is compared with the color pattern at theunit of 7 pixels, and sends the ghost data to the control section 230.

Table 3 shows an example of the color ghost table in a normal readingmode.

                                      TABLE 3                                     __________________________________________________________________________           Color Pattern                                                                            Target          Ghost                                       Number Peripheral Pixel                                                                         Pixel                                                                              Peripheral Pixel                                                                         Data                                        __________________________________________________________________________    1      White White Blue                                                                         Blue Black Black Black                                                                        11                                          2      White White Blue                                                                         Blue White White White                                                                        00                                          3      White White White                                                                        Red  Black Black Black                                                                        11                                          4      White White Red                                                                          Red  Red White White                                                                          00                                          __________________________________________________________________________

In table 3, numerals show the order of disposition to be written in thecolor ghost table. This order of disposition is mainly used in the caseof correction. The color pattern shows a color code signal row forcomparing the target pixel with the 6 peripheral pixels. Ghost data isadded forming a pair with the color pattern. For example, the colorghost detecting means 234 operates in the following manner. When a colorcode signal row corresponding to 7 pixels sent out from the distributionmeans S coincides with the color pattern shown by numerals 1 and 3, theghost data "11" showing the occurrence of color ghost at the edge of ablack image.

On the other hand, when the color ghost detecting means 234 detects thatthe color code signal row corresponding to the 7 pixels sent out fromthe distribution means S has coincided with the color patterns shown bythe numerals 2 and 4, the ghost data "00" showing that there is no colorghost is sent out.

The control section 230 operates as follows. First, the effective datais adopted in the following manner. Sampling data is obtained bypreliminary scanning. In the sampling data, digital image data in aregion except for a black region in the color separation map shown inFIG. 8 is used as the effective data, wherein the digital image data iscolor information, the frequency of which exceeds that of the colorghost. Specifically, in order to make a histogram showing the densitydistribution for each color code as illustrated in FIG. 10, a densitycode counter NC for counting the density code is provided, and also aghost counter GC for counting the frequency of color ghost is provided.When these counters are provided, a histogram for showing the densitydistribution for each color code is made. The frequency corresponding tocolor ghost is subtracted from the histogram of a color region exceptfor the color code "00". According to the histogram on which thesubtraction has been conducted, discrimination processing is carried outfor discriminating the document OG placed on the platen glass PG fromthe specific document.

In this connection, the control section 230 conducts, the ACSprocessing, EE processing and APS processing. In the ACS processing, thecolor codes of red, blue and black are counted by pre-scanning so thatthe document color is judged. In the EE processing, in order toautomatically copy in accordance with the document density, anappropriate density compensation pattern is selected from the documentdensity histogram, that is, what is called a gamma table is selected. Inthe APS processing, when the number of yellow bands of the platen coveris counted, the document size is detected. Explanations of theaforementioned processing will be omitted here.

With reference to FIGS. 9, 10 and 15, the operation of pre-scanning ofthe image reproducing apparatus 200 of this example will be explained asfollows.

First, the operator opens the platen cover and puts the document OG onthe platen glass PG. Then the operator sets the number of copies usingthe operation panel 210, and presses the copy switch. As illustrated inFIG. 15, the control section 230 turns on the light source 202. Then thelight source 202 is moved at a predetermined speed while the lightsource 202 illuminates the surface of the document OG with white light,the illuminated portion being formed rectangular. The control section230 moves the V mirror section M22 at half the speed of the light source202 in the same direction as that of the light source 202. Due to theforegoing, the document OG is scanned. A beam of light reflected on thesurface of the document OG is reflected by the first, second and thirdmirrors 203, 204, 205. Then the beam of light is divided into a red anda cyan component by the action of the dichroic mirror DM. Then a redimage is formed on the red line sensor LS1 by the image formation lens206, and a cyan image is formed on the cyan line sensor LS2. Thescanning conducted by the image reading section AA is the pre-scanningconducted before the image formation process.

A sampling range for discrimination processing is 100 mm in the primaryscanning direction shown by hatched lines in FIG. 7, and 162 mm in thesubsidiary scanning direction. For example, data is sampled for each 1mm in the primary scanning direction and 0.25 mm in the subsidiaryscanning direction. Accordingly, sampling data of 64800 points can beobtained.

Electric currents I_(R) and I_(C) outputted from the red and cyan linesensors LS1 and LS2 in the pre-scanning, are respectively subjected toshading compensation by the A/D converters AD1 and AD2. At the sametime, the currents are subjected to the A/D conversion, so that thecurrents are converted into the digital image signals V_(r) and VC of 6bits, and then the image signals are sent to the color separation table231A. The color separation table 231A sends a color signal of 8 bitscorresponding to the digital image signal to the distribution means S.The distribution means S sends only the color code to the color ghostdetecting means 234, and synchronously sends a color signal of 8 bits tothe control section 230.

When the color ghost detecting means 234 detects that a color codesignal row corresponding to 7 pixels sent out from the distributionmeans S has coincided with the color patterns of numerals 1 and 3 shownon Table 3, the ghost data "11" showing that color ghost has occurred atthe edge of a black image is sent out to the control section 230.

When the color ghost detecting means 234 detects that a color codesignal row corresponding to 7 pixels sent out from the distributionmeans S has coincided with the color patterns of numerals 2 and 4 shownon Table 3, the ghost data "00" showing that there is no color ghost issent out to the control section 230.

The control section 230 operates as follows. The sampling dot number ofthe density code, the value of which is the same for each color code, iscounted by the density code counter NC, and the histogram of densitylevel is is made. On the other hand, the control section 230 counts theghost data caused in a region except for the black region in the colorseparation map, by the ghost counter GC. The control section 230compares the effective color data, which is subtracted the sampling dotnumber corresponding the color ghost from the histogram data, with thefrequency data that has been previously set. In this way, the documentOG placed on the platen glass PG is discriminated from the specificdocument. Due to the foregoing, the specific document is discriminatedwithout being affected by (1) the mounting accuracy of the CCD, and theslippage of pixels caused by the deformation and lapse of time of theCCD, (2) disagreement of the magnification of red and blue, and MTF, and(3) color ghost caused by the level difference between the outputs ofred and blue caused by chromatic aberration. Further, without comparingcomplicated patterns, the specific document can be discriminated. Thepresent invention provides an image reproducing apparatus having theaforementioned characteristics.

An example of the image reproducing apparatus to accomplish the thirdobject of the present invention will be explained as follows.

FIG. 11 is a block diagram showing an outline of the construction of anexample of the image reproducing apparatus to accomplish the thirdobject of the present invention . FIG. 12 is a block diagram showing anoutline of the construction of the signal extraction circuit.

As illustrated in FIG. 11, the image reproducing apparatus 200 of thisexample includes the image reading section AA by which the document OGplaced on the platen 201 is subjected to color separation so that theimage is digitally read out. By a digital signal sent out from the imagereading section AA, the color is separated to the recording color, andthe color image is reproduced. The image reproducing apparatus 200 ofthe present invention includes the first counter CNT1, the secondcounter CNT2, and the comparing means CMP. In this case, the firstcounter CNT1 stores the specific color region data showing a colorregion corresponding to the color of the specific mark attached to thespecific document, and also stores the specific mark frequency datashowing the sampling data number composing the specific mark attached tothe specific document. The second counter CNT2 counts the totalfrequency of the sampled digital image data in the specific colorregion. The comparing means CMP compares the count value of the secondcounter CNT2 with the specific frequency data. When the imagereproducing apparatus 200 of the present invention includes the firstcounter CNT1, the second counter CNT2, and the comparing means CMP asdescribed above, the specific mark is specified in the color region inthe color separation map shown in FIG. 13, and in the dot numbercomposing the specific mark. In this case, the second counter CNT2 maycount the sampling dot number except for the outer frame of the specificmark, or alternatively, the second counter CNT2 may count the samplingdot number including the outer frame of the specific mark. A blurredimage detecting means 236 detects a blurred image on the outer framecomposing the specific mark, and a discontinued image compensation means237 compensates at least one of the primary scanning and the subsidiaryscanning in accordance with the output signal sent from the blurredimage detecting means 236. Due to the aforementioned blurred imagedetection means 236 and the discontinued image compensation means 237,the optical accuracy of the image reproducing apparatus can be preventedfrom being deteriorated, and the specific mark can be recognized moreefficiently even in the case of misoperation.

Construction of the image reading means AA has already been explainedwith reference to FIGS. 5 and 15. Therefore, the explanations will beomitted here. In this case, the document OG is placed on the platenglass PG. The cut-off frequency of the dichroic mirror DM is about 540nm. Due to the foregoing, a red component is transmitted and a cyancomponent is reflected. In accordance with the intensity of receivedlight, the line sensors LS1 and LS2 outputs the electric currents I_(R)and I_(C).

The image processing section BB is newly constructed as describedbefore. The image processing section BB includes a blurred imagecompensation image 236, discontinued image compensation means 237, andregion detecting means 238. The blurred image compensation image 236 isconnected with a signal extraction means 239 through an MTF compensationmeans 233.

The color separation table 231A is provided with a high speed ROM, andas illustrated in the color separation map shown in FIG. 10,predetermined data is written in the color separation table 231A.Specifically, color signal data of 8 bits relating to the recordingcolor corresponding to the digital image signals V_(r) and V_(c) of 6bits is written on the color separation table 231A. In this case, thedigital image signal V_(r) of 6 bits shows the density level of a redcomponent, and the digital image signal V_(c) of 6 bits shows thedensity level of a cyan component. In this case, the color signal datarelating to the recording color composing the color separation table231A includes: color code data of 2 bits for designating the developercolor; specific code data of 1 bit showing the specific color; anddensity data of 5 bits for determining the density of the recordingcolor. Consequently, the color separation table 231A outputs the data ofthe recording color in the form of a color signal.

In this connection, the color separation table 231A is exclusively usedfor pre-scanning. In this example, a color separation table exclusivelyused for image formation is provided, the detailed explanation of whichwill be omitted here.

The specific code data is defined as code data expressing the wavelength component of the background color on the specific document orexpressing the wave length component of light reflected by the color ofa specific mark attached on the specific document. In this case, thespecific mark is composed of a character or a symbol, and an outerframe. Any mark may be used for the specific mark as long as it can bediscriminated to be red or blue on the color separation map. The numberof bits of the specific mark corresponds to LMB in the color code data.

The color code is determined by the specification. For example, thecolor code is shown in Table 4.

                  TABLE 4                                                         ______________________________________                                                     Color Code                                                       Color          Specific Code                                                  ______________________________________                                        Black          0          00                                                  Blue           0          01                                                  Red            0          10                                                  Red            1          10                                                  White          0          11                                                  ______________________________________                                    

According to the color separation map shown in FIG. 10, the specificcolor region is provided in the red region. Therefore, the color code is"110". However, the specific color region is not limited to thisspecific example. The specific region can be set in any regions on thecolor separation map shown in FIG. 10. Further, a plurality of regionscan be set by the setting means 232 shown in FIG. 9.

The density data can be expressed by the following expression.

    (Density data)=(V.sub.r +V.sub.c)/2

As expressed by the above expression, the density data is found when thedensity level of the cyan component and that of the red component areaveraged.

When the color separation table 231A is constructed in the mannerdescribed above, a color signal of 8 bits can be outputted which iscomposed of color code data and density data corresponding to therecording color determined by the digital image signals V_(r) and V_(c).

The blurred image compensation means 236 operates as follows. Color codedata for compensating a blurred image is written in a high speed ROM,which will be referred to as a blurred image compensation ROM,hereinafter. A color region relating to the target pixel is determinedby LMB in a color code data row corresponding to 7 pixels sent out fromthe color separation table 231a. An address in the memory region in theROM is determined from the color code data row corresponding to the 6residual pixels. In this way, data is corrected to the color code datastored in the address. Specifically, the blurred image compensationmeans 236 operates in such a manner that white is corrected to the framecolor when the number of white pixels surrounded by the frame color isnot more than 3. Using the blurred image compensation patterns for 1 to3 dots shown in FIGS. 8 to 10, when the primary scanning and subsidiaryscanning are coincident, white is corrected to the frame color, and thecolor signal is sent out to the discontinued image compensation means237 and MTF compensation means 233. The compensation pattern may bechanged over while the compensation pattern is also used for color ghostcompensation. Since the color ghost compensation has been describedbefore, the detailed explanation will be omitted here.

With reference to Tables 5 to 7, a relation between address and data inthe blurred image compensation ROM will be explained as follows.

                                      TABLE 5                                     __________________________________________________________________________    Number of                         Result                                      dots of                           of                                          compensa-                         compen-                                                                            Ad-                                    tion  S7  S6  S5  S4  S3  S2  S1  sation                                                                             dress                                                                             Data                               __________________________________________________________________________    1 dot                                                                             (1)                                                                             White                                                                             Blue                                                                              Blue                                                                              White                                                                             Blue                                                                              Blue                                                                              Blue                                                                              Blue 5D5 DD                                       /Blue                                                                       (2)                                                                             White                                                                             Blue                                                                              Blue                                                                              White                                                                             Blue                                                                              Blue                                                                              Blue                                                                              Blue 5D7 DD                                       /Blue                                                                       (3)                                                                             White                                                                             Blue                                                                              Blue                                                                              White                                                                             Blue                                                                              White                                                                             Blue                                                                              Blue 5DD DD                                       /Blue                                                                       (4)                                                                             White                                                                             Blue                                                                              Blue                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             Blue 5DF DD                                       /Blue                                                                       (5)                                                                             White                                                                             White                                                                             Blue                                                                              White                                                                             Blue                                                                              Blue                                                                              Blue                                                                              Blue DD5 DD                                       /Blue                                                                       (6)                                                                             White                                                                             White                                                                             Blue                                                                              White                                                                             Blue                                                                              Blue                                                                              Blue                                                                              Blue DD7 DD                                       /Blue                                                                       (7)                                                                             White                                                                             White                                                                             Blue                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             Blue DDD DD                                       /Blue                                                                       (8)                                                                             White                                                                             White                                                                             Blue                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             Blue DDF DD                                       /Blue                                                                   1 dot                                                                             (9)                                                                             White                                                                             Red Red White                                                                             Red Red Red Red  AEA FA                                       /Red                                                                       (10)                                                                             White                                                                             Red Red White                                                                             Red Red Red Red  AEB FA                                       /Red                                                                       (11)                                                                             White                                                                             Red Red White                                                                             Red White                                                                             Red Red  AEE FA                                       /Red                                                                       (12)                                                                             White                                                                             Red Red White                                                                             Red White                                                                             White                                                                             Red  AEF FA                                       /Red                                                                       (13)                                                                             White                                                                             White                                                                             Red White                                                                             Red Red Red Red  EEA FA                                       /Red                                                                       (14)                                                                             White                                                                             White                                                                             Red White                                                                             Red Red Red Red  EEB FA                                       /Red                                                                       (15)                                                                             White                                                                             White                                                                             Red White                                                                             Red White                                                                             White                                                                             Red  EEE FA                                       /Red                                                                       (16)                                                                             White                                                                             White                                                                             Red White                                                                             Red White                                                                             White                                                                             Red  EEF FA                                       /Red                                                                    __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________    Number of                         Result                                      dots of                           of                                          compensa-                         compen-                                                                            Ad-                                    tion  S7  S6  S5  S4  S3  S2  S1  sation                                                                             dress                                                                             Data                               __________________________________________________________________________    2 dot                                                                             (1)                                                                             White                                                                             Blue                                                                              Blue                                                                              White                                                                             White                                                                             Blue                                                                              Blue                                                                              Blue 5F5 DD                                       /Blue                                                                      (2)                                                                              White                                                                             Blue                                                                              Blue                                                                              White                                                                             White                                                                             Blue                                                                              White                                                                             Blue 5F7 DD                                       /Blue                                                                      (3)                                                                              White                                                                             White                                                                             Blue                                                                              White                                                                             White                                                                             Blue                                                                              Blue                                                                              Blue DF5 DD                                       /Blue                                                                      (4)                                                                              White                                                                             White                                                                             Blue                                                                              White                                                                             White                                                                             Blue                                                                              White                                                                             Blue DF7 DD                                       /Blue                                                                      (5)                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             Blue                                                                              Blue                                                                              Blue                                                                              Blue 7D5 DD                                       /Blue                                                                      (6)                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             Blue                                                                              Blue                                                                              White                                                                             Blue 7D7 DD                                       /Blue                                                                      (7)                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             Blue                                                                              White                                                                             Blue                                                                              Blue 7DD DD                                       /Blue                                                                      (8)                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             Blue                                                                              White                                                                             White                                                                             Blue 7DF DD                                       /Blue                                                                   3 dot                                                                            (1)                                                                              White                                                                             Blue                                                                              Blue                                                                              White                                                                             White                                                                             Blue                                                                              Blue                                                                              Blue 5FD DD                                       /Blue                                                                      (2)                                                                              White                                                                             White                                                                             Blue                                                                              White                                                                             White                                                                             White                                                                             Blue                                                                              Blue DFD DD                                       /Blue                                                                      (3)                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             White                                                                             Blue                                                                              Blue                                                                              Blue 7F5 DD                                       /Blue                                                                      (4)                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             White                                                                             Blue                                                                              White                                                                             Blue 7F7 DD                                       /Blue                                                                      (5)                                                                              Blue                                                                              White                                                                             White                                                                             White                                                                             Blue                                                                              Blue                                                                              Blue                                                                              Blue FD5 DF                                    (6)                                                                              Blue                                                                              White                                                                             White                                                                             White                                                                             Blue                                                                              Blue                                                                              White                                                                             Blue FD7 DF                                    (7)                                                                              Blue                                                                              White                                                                             White                                                                             White                                                                             Blue                                                                              White                                                                             Blue                                                                              Blue FDD DF                                    (8)                                                                              Blue                                                                              White                                                                             White                                                                             White                                                                             Blue                                                                              White                                                                             Blue                                                                              Blue FDF DF                                 __________________________________________________________________________

In this example, it is possible to write a look-up table correspondingto the all color region on a single ROM, however, consideration is givento the convenience of correction conducted later, and a look-up tablefor each color is written in an independent memory region, for example,in an individual ROM. In this case, data S7 is data used for directing acolor region or a ROM corresponding to the color region. For example,white/blue may show a white region or a ROM in which the white region iswritten, or it may show a blue region or a ROM in which the blue regionis written.

In Tables 5 and 6, data of the look-up table includes: color code datarows S1 to S6 corresponding to the address data in the memory region ofthe ROM; and color code data for correcting the color code of the targetpixel. For example, in a table corresponding to the dot number 1 ofcorrection, data S4 is color code data corresponding to the targetpixel. Data S1 to S3, S5 and S6 are color code data corresponding to theperipheral pixel.

The dot number of correction shows the number of dots, the color codesof which are to be corrected.

                                      TABLE 7                                     __________________________________________________________________________    Number of                         Result                                      dots of                           of                                          compensa-                         compen-                                                                            Ad-                                    tion  S7  S6  S5  S4  S3  S2  S1  sation                                                                             dress                                                                             Data                               __________________________________________________________________________    1 dot                                                                             (1)                                                                             White                                                                             Blue                                                                              White                                                                             Blue                                                                              White                                                                             Blue                                                                              Blue                                                                              Blue 775 DD                                       /Blue                                                                      (2)                                                                              White                                                                             Blue                                                                              White                                                                             Blue                                                                              White                                                                             Blue                                                                              White                                                                             Blue 777 DD                                       /Blue                                                                      (3)                                                                              White                                                                             Blue                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             Blue                                                                              Blue 77D DD                                       /Blue                                                                      (4)                                                                              White                                                                             Blue                                                                              White                                                                             Blue                                                                              White                                                                             White                                                                             White                                                                             Blue 77F DD                                       /Blue                                                                   1 dot                                                                            (5)                                                                              White                                                                             Red White                                                                             Red White                                                                             Red Red Red  BBA FA                                       /Red                                                                       (6)                                                                              White                                                                             Red White                                                                             Red White                                                                             Red White                                                                             Red  BBB FA                                       /Red                                                                       (7)                                                                              White                                                                             Red White                                                                             Red White                                                                             White                                                                             Red Red  BBE FA                                       /Red                                                                       (8)                                                                              White                                                                             Red White                                                                             Red White                                                                             White                                                                             White                                                                             Red  BBF FA                                       /Red                                                                    __________________________________________________________________________

Table 7 is approximately the same as Tables 5 and 6. A compensationpattern for compensating bug is shown in Table 7.

                                      TABLE 8                                     __________________________________________________________________________    Pattern for compensating 1 dot                                                Target pixel                                                                  __________________________________________________________________________    White/Red                                                                           White/Red                                                                            Red White                                                                              Red White/Red                                                                            White/Red                                    __________________________________________________________________________

                                      TABLE 9                                     __________________________________________________________________________    Pattern for compensating 2 dots                                               __________________________________________________________________________    Target pixel                                                                  __________________________________________________________________________    White/Red                                                                           White/Red                                                                            Red White                                                                              White                                                                             Red    White/Red                                    Target pixel                                                                  __________________________________________________________________________    White/Red                                                                           Red    White                                                                             White                                                                              Red White/Red                                                                            White/Red                                    __________________________________________________________________________

                                      TABLE 10                                    __________________________________________________________________________    Pattern for compensating 3 dots                                               __________________________________________________________________________    Target pixel                                                                  __________________________________________________________________________    White/Red                                                                           White/Red                                                                            Red White                                                                              White                                                                             White  Red                                          Target pixel                                                                  __________________________________________________________________________    White/Red                                                                           Red    White                                                                             White                                                                              White                                                                             Red    White/Red                                    Target pixel                                                                  __________________________________________________________________________    Red   White  White                                                                             White                                                                              Red White/Red                                                                            White/Red                                    __________________________________________________________________________

The discontinued image compensation means 237 recognizes the time atwhich the frame line crosses the character, and then conductscompensation processing. In the case where the frame line width is notless than 5 dots, specifically, when the same discontinued imagecompensation pattern shown in Table 11 is coincident with respect to theprimary scanning and the subsidiary scanning, the line and charactercoming into contact with the frame line are compensated in the primaryand subsidiary directions by 0.5 mm.

                  TABLE 11                                                        ______________________________________                                        1   2     3     4   5   6   7    8   9   10  11  12                                                    13  14    15                                         ______________________________________                                        B   R     R     R   R   R   x    x   x   x   x   x                                                     x   x     x                                                                   B   B     R R R R R x x x x x x x x                                           B   B     B R R R R R x x x x x x x                                           B   B     B B R R R R R x x x x x x                                           B   B     B B B R R R R R x x x x x                                           B   B     B B B B R R R R R x x x x                                           B   B     B B B B B R R R R R x x x                                           B   B     B B B B B B R R R R R x x                                           R                                                    ______________________________________                                         B: Black R: Red                                                          

Table 11 shows the rows of dots in the primary or subsidiary scanningdirection. The size of 8 dots corresponds to the length of 0.5 mm on adocument. Character x in Table 11 shows that there is no color codedata, or alternatively it shows dummy data. In Table 11, numerals 1 to15 are discrimination numbers of the discontinued image compensationpatterns. The discrimination numbers 9 to 13 express the color codescorresponding to the size of the frame line that can not be corrected.The discrimination numbers 1 to 8 express the color codes correspondingto the size of the frame line that can be corrected.

The region detection means 238 reads a detecting portion of the frameline as "1" and also reads other portions as "0", so that the region onthe present line is determined. A region corresponding to the first riseand the last transition of the reading information having a commonportion with respect to the region on all line, is "1" and other regionsare "0". In this way, a converting region signal of the region signaland the reading information is sent out to the signal extraction circuit239. This processing is repeated for each line at real time.

As illustrated in FIG. 12, the signal extraction circuit 239 includes aframe line inside and outside detection circuit 239A, mode control 239Band density data detecting circuit 239C. The signal extraction circuit239 extracts the density data of pixels designated as a color regionsignal and a processing mode signal.

The frame line inside and outside detecting circuit 239A judges theregion signals RQN and BQN sent out from the region detecting means 238,and detects whether a dot is inside or outside of the frame line. Forexample, it is indicated by the frame line inside and outside detectingcircuit 239A whether an image signal sent out from the MTF compensationmeans 233 is inside or outside of the frame line composing the specificmark.

The mode control 239B is directed by the operation panel 210, and thepixel selecting signal DSS is sent out from the mode control 239B. Inthis case, the pixel selecting signal DSS directs whether the pixel isextracted from the inside of the frame line or the pixel is extractedfrom the outside of the frame line, wherein the direction is given bythe mode signal for designating a marker mode, reversal mode or normalmode, and also the direction is given by the output signal sent out fromthe frame line inside and outside detecting circuit 239A.

The density data detecting circuit 239C sends out the density signal andcolor code signal of the pixel selected in accordance with the imageselecting signal DSS to the control section 230. For example, a colorcode of the image signal sent out from the MTF compensation means 233 isoutputted to the mode control 239B and control section 230, and adensity signal is inputted into the selection circuit 239CC through thebuffers 239CA and 239CB. The selection circuit 239CC selectively sendsout the density data to the control section 230 in accordance with thepixel selecting signal DSS.

While consideration is given to the real time processing conducted inthe hardware in this example, the MTF compensation means 233 uses aconvolution filter, the size of which is 3×3. In this case, convolutionis described as follows. Image data and a digital-matrix-likeconvolution filter are mutually correlated, so that the same componentas the arrangement of values in the matrix is extracted from the imagedata. An example of the convolution filter of 3×3 will be explained asfollows with reference to Tables 12 and 13.

                  TABLE 12                                                        ______________________________________                                        Character Type Document                                                       ______________________________________                                        0               -1     0                                                      -1/2             4     -1/2                                                   0               -1     0                                                      ______________________________________                                    

Table 12 shows an example of the convolution filter for use in acharacter type document.

                  TABLE 13                                                        ______________________________________                                        Photograph Type Document                                                      ______________________________________                                        0               -1/4   0                                                      -1/4            2      -1/4                                                   0               -1/3   0                                                      ______________________________________                                    

Table 13 shows an example of the convolution filter for use in aphotograph type document.

The control section 230 includes: specific color region data for showinga color region corresponding to the color of a specific mark attached toa document; a first counter CNT1 for storing specific mark frequencydata showing the number of sampling data composing the specific markattached to the document; a second counter CNT2 for counting the totalfrequency of digital image data in the specific color region of thedigital image data; and a comparison means CMP for comparing a countvalue of the second counter CNT2 with the specific frequency data. Whenthe aforementioned control section 230 is provided, the specific markcan be specified from the color region shown in the color separation mapin FIG. 10, and also can be specified from the number of dots composingthe specific mark. The second counter CNT2 may count the number ofsampling dots of the specific mark except for the outer frame. Thesecond counter CNT2 may count the number of sampling dots of thespecific mark including the outer frame composing the specific mark. Inthis case, the specific color data includes a color code expressing thecolor region, and density data. The specific color data is data forspecifying the color region shown in the color separation map in FIG.10, from the density and color region.

With reference to FIGS. 7, 10 to 12, and 15, the pre-scanning operationof the image reproducing apparatus 200 of this example will be explainedas follows.

First, the operator opens the platen cover PK and puts the document OGon the platen glass PG. Then the operator sets the number of copiesusing the operation panel 210, and presses the copy switch. Asillustrated in FIG. 15, the control section 230 turns on the lightsource 202. Then the light source 202 is moved at a predetermined speedwhile the light source 202 illuminates the surface of the document OGwith white light, the illuminated portion being formed rectangular. Thecontrol section 230 moves the V mirror section M22 at half the speed ofthe light source 202 in the same direction as that of the light source202. Due to the foregoing, the document OG is scanned. A beam of lightreflected on the surface of the document OG is reflected by the first,second and third mirrors 203, 204, 205. Then the beam of light isdivided into a red and a cyan component by the action of the dichroicmirror DM. Then a red image is formed on the red line sensor LS1 by theimage formation lens 206, and a cyan image is formed on the cyan linesensor LS2. The scanning conducted by the image reading section AA isthe pre-scanning conducted before the image formation process.

A sampling range for discrimination processing is 100 mm in the primaryscanning direction shown by hatched lines in FIG. 7, and 162 mm in thesubsidiary scanning direction. For example, data is sampled for each 1mm in the primary scanning direction and 0.25 mm in the subsidiaryscanning direction. Accordingly, sampling data of 64800 points can beobtained. EE processing and APS processing are also carried out as thepre-scanning operation in this example, however, the detailedexplanations will be omitted here.

Electric currents I_(R) and I_(C) outputted from the red and cyan linesensors LS1 and LS2 in the pre-scanning, are respectively subjected toshading compensation by the A/D converters AD1 and AD2. At the sametime, the currents are subjected to the A/D conversion, so that thecurrents are converted into the digital image signals V_(r) and V_(C) of6 bits, and then the image signals are sent to the color separationtable 231A. The color separation table 231A sends a color signal of 8bits corresponding to the digital image signal to the blurred imagecompensation means 236.

Data S7 is LMB in the color code data row corresponding to the 7 pixelssent out from the color separation table 231A. The blurred imagecompensation means 236 determines a color region relating to the targetpixel by the data S7. The blurred image compensation means 236 selectsthe blurred image compensation ROM corresponding to the color region.Then the blurred image compensation means 236 compares a color code datarow corresponding to the 6 residual pixels with the compensationpatterns S1 to S6 shown in Table 5. In the case where the color codedata row corresponding to the 6 pixels does not coincide with thecompensation patterns S1 to S6 shown in Table 5, the blurred imagecompensation means 236 sends the color signal as it is, to thediscontinued image compensation means 237 and the MTF compensation means233. On the other hand, in the case where the color code data rowcorresponding to the 6 pixels coincides with the compensation patternsS1 to S6 shown in Table 5, the blurred image compensation means 236determines the address in the memory region of the selected blurredimage compensation ROM, and the data is corrected to the color code datashowing the color code accommodated in the address. Specifically, theblurred image compensation means 236 corrects white to a frame linecolor in the case where white surrounded by the frame line color is notmore than 3 pixels. Using the blurred image compensation patterns for 1to 3 dots shown in Tables 8 to 10, when both primary scanning andsubsidiary scanning are coincident, white is corrected to the frame linecolor, and the color signal is sent out to the discontinued imagecompensation means 237 and MTF compensation means 233. Due to theforegoing, as shown by the compensation result in Table 5, when thecolor code is corrected, the blurred image compensation can be carriedout.

The discontinued image compensation means 237 detects whether or not thecolor code row in the color signal sent out from the blurred imagecompensation means 236 coincides with the same compensation patternshown in Table 12 with respect to the primary and subsidiary scanning.In the case where they are coincident, under the condition that thewidth of the frame line is not less than 5 dots, the color code in thecolor signal corresponding to the target pixel is corrected to the frameline color, and the corrected color code is sent out to the regiondetecting means 238. Due to the foregoing operation, a line andcharacter coming into contact with the frame line can be compensated inthe directions of primary and subsidiary scanning by 0.5 mm.

In accordance with the color code sent out from the discontinued imagecompensation means 237, the region detecting means 238 reads a detectedportion of the frame line color as "1" and the region detecting means238 reads other portions of the frame line color as "0". In this way, aregion at the present line is determined. A region corresponding to thefirst rise and the last transition of the reading information having acommon portion with respect to the region on all line, is "1" and otherregions are "0". In this way, a converting region signal of the regionsignal and the reading information is sent out to the signal extractioncircuit 239. This processing is repeated for each line at real time.

In accordance with the mode designation signal sent from the operationpanel 210, the MTF compensation means 233 uses the convolution filter of3×3 for use in character type documents shown in Table 7 or for use inphotograph type documents shown in Table 8, and extracts the samecomponent as the value arrangement in the matrix, from the density data.An 8 bit color signal obtained in this way is sent to the signalextraction circuit 239.

The frame line inside and outside detecting circuit 239A judges theregion signals RQN and BQN sent out from the region detecting means 238,and detects whether a color signal sent out from the MTF compensationmeans 233 is inside or outside of the frame line composing the specificmark. Then an inside and outside signal indicating whether the colorsignal sent out from the MTF compensation means 233 is inside or outsideof the frame line, is sent to the mode control 239B.

In accordance with the mode signal and the inside and outside signaldirected through the operation panel 210 shown in FIG. 11, the modecontrol 239B sends the pixel selection signal DSS to the density datadetecting circuit 239C, wherein the pixel selection signal DSSdesignates whether the pixel is extracted from the inside of the frameline or the outside of the frame line.

The density data detecting circuit 239C sends the density data signaland color code signal of the pixel selected in accordance with the imageselection signal DSS, to the control section 230. For example, the colorcode of the image signal sent out from the MTF compensation means 233 isoutputted into the mode control 239B and control section 230, and thedensity data signal is inputted into the selection circuit 239CC throughthe buffers 239CA and 239CB. The selection circuit 239CC selectivelysends the density data to the control section 230 in accordance with thepixel selection signal DSS. In the case where the pixel selection signalDSS designates the inside of the frame line, a color signal inside theframe line composing the specific mark is extracted from the colorseparation table 231B and sent to the control section 230. In the casewhere the image selection signal does not designate either the inside orthe outside of the frame line, the signal extraction circuit 239 doesnot extract a color signal and sends the signal as it is. For theconvenience of explanation, this color signal is referred to as anon-extraction color signal.

The control section 230 compares the non-extraction color signal sentout from the density data detecting circuit 239C, with the specificcolor region data. In the case where they are not coincident with eachother, the control section 230 does not increase the first counter CNT1.In the case where they are coincident with each other, the controlsection 230 increases the first counter CNT1. Due to the foregoing,specific mark frequency data showing the number of sampling datacomposing the specific mark attached to the specific document, can bestored in the first counter CNT1.

The control section 230 compares an extraction color signal sent outfrom the density data detecting circuit 230C with the specific colorregion data. Only when they are coincident with each other, the secondcounter CNT2 is increased. Due to the foregoing, the frequency of dotscomposing the character or sign except for the frame line composing thespecific mark, is stored in the second counter CNT2.

By the control of the control section 230, the comparing means CMPcompares the count value stored in the second counter CNT2 with thespecific frequency data. When they are coincident, it can be recognizedthat the document OG is the specific document. In this way, by thecontrol of the control section 230, the document OG and the specificdocument can be discriminated by the color region in the colordiscrimination map in FIG. 13 and the number of dots composing thespecific mark. In the case where they are not coincident in thecomparing operation described above, it is judged that the document OGis not the specific document.

In this example, the second counter CNT2 increases the number ofsampling dots of the specific mark except for the outer frame, however,the present invention is not limited to the specific example. The numberof sampling dots may be increased including the frame line composing thespecific mark.

As described above, the image reproducing apparatus 200 of this exampleonly has the specific color region data in the color separation mapshown in FIG. 10, and the number of dots composing the specific mark, asdata for discriminating the specific document. Accordingly, thedeterioration of copying function can be prevented although a largenumber of specific documents are registered. Further, the imagereproducing apparatus 200 of this example includes the blurred imagecompensation means 236 and discontinued image compensation means 237.Therefore, an image reproducing apparatus can be provided, by which thespecific document can be positively prevented from being copied withoutbeing affected by a blurred specific mark caused by the deterioration ofthe MTF characteristics.

In the image reproducing apparatus 200 of this example, ghostcompensation is not conducted. However, when ghost compensation is alsocarried out, the specific document can be positively discriminatedwithout being affected by the following factors.

(1) Slippage of pixels caused between CCDs originated from the mountingaccuracy of the CCDs, deformation of the CCDs, and a change in the CCDscaused by lapse of time

(2) Disagreement of the magnification of red, blue and MTF.

(3) Color ghost originated from the output level difference between redand blue caused by chromatic aberration of the lens

With reference to FIG. 7 and FIGS. 13 to 15, an example of the imagereproducing apparatus to accomplish the fourth object of the presentinvention will be explained as follows.

As illustrated in FIG. 15, what is called a KNC process type digitalsystem is adopted in the image reproducing apparatus 200 of thisexample, and the image reproducing apparatus 200 comprises: a platen 201made of platen glass (referred to as platen glass PG in this examplehereinafter); a light source 202 for illuminating a document OG placedon the platen 201 with a beam of white light; a first mirror 203 mountedon a moving member M1 having the light source 202, wherein the firstmirror 203 reflects a beam of light sent from the document OG; a Vmirror unit M22 including a second mirror 204 and third mirror 205 whichreflect the beam of light sent from the first mirror 203; and an imageformation lens 206 through which an image is formed on a line sensor LS1for red and a line sensor LS2 for cyan through a dichroic mirror (shownby DM in FIG. 5). These units compose an image reading section AA. Theimage reproducing apparatus 200 also comprises: an image processingsection BB in which a digital image signal sent from the image readingsection AA is converted into a color signal corresponding to a recordingcolor; a writing section CC which emits a laser beam in accordance witha recording signal and conducts scanning on the image forming body 220for each dot; an image formation processing section DD including ascorotron charger 221, developing units 222Y, 222M, 222C, 222BK,transfer unit 2223, separating unit 2224, and cleaning unit 225, whereinelectrostatic photographic processing is carried out in the imageformation processing section DD; and a sheet feeding system EE whichfeeds recording sheets P to the transfer and separation sections. Whenthe electrostatic photographing processing is carried out in the aboveapparatus, a color image of the document is reproduced on the recordingsheet P.

In this case, the image forming body 220 is a drum, the diameter ofwhich is approximately 100 mm. In the image forming body 220, an OPCphotosensitive layer is formed in an aluminum base.

As a new construction, the image reproducing apparatus 200 includes: acolor separation table 231A composing the first judging means whichoutputs a signal for judging the coincidence with the original (thefirst generation) of the specific document; and a color separation table231B composing the second judging means which judges an indication colorfor indicating the second generation, wherein the indication color iswritten when the second generation copy has been made from the specificdocument. This image reproducing apparatus 200 includes: a controlsection 230 composing a warning and prohibiting means, wherein thewarning and prohibiting means gives warning in accordance with an outputsignal sent from the color separation table 231A or 231B, and also thewarning and prohibiting means prohibits the copying operation, thegeneration of which exceeds a predetermined one; and a control panel 210composing a releasing means for releasing the warning indication or theprohibition of generation copy.

In this example, it is supposed that recording sheets having a specificbackground color such as red are used for the original of the specificdocument and that a specific mark such as a letter and mark is writtenin the original. In this case, when the first judging means is used, itis judged whether or not a document to be reproduced is the original ofthe specific document (the first generation document). In enterprises,the specific document is allowed to be copied only once so that thecopies can be distributed to the departments concerned. In this case,the copying operation of the second generation is not allowed, and it isnecessary that the prohibition of generation copy can not be withdrawnby any methods such as a control key or ID card. In this example, whenthe second judging means is used, it is judged whether or not a documentto be reproduced is the copy of the second generation of the specificdocument.

Specifically, when a specific color code signal sent from the colorseparation table 231A composing the first judging means, is "1" it canbe judged that the document is the original of the specific document.Therefore, the image reproducing apparatus 200 gives warning once.However, when the control key 0r ID is used, the prohibition can bewithdrawn, so that the second generation copying operation can beexecuted using a release switch.

In the case where the second generation copy is made, it is checked byvarious methods that the copy is of the second generation, and the copyof the following generation is positively prohibited. In an embodimentof the present invention, as illustrated in FIG. 16, using a developingunit such as a developing unit 222Y, 222M or 222C which is not a blackdeveloping unit, a row of indication characters expressing the secondgeneration are written in addition to the document image to be copied.For example, the row of indication characters "Confidential" are printedin yellow on the background so that the second generation copy isexpressed while the document image can be clearly recognized.

In the manner described above, on the background of the specificdocument of the second generation, a row of indication characterspeculiar to the second generation are printed. Therefore, when thefollowing generation document is made from the second generationdocument, the row of indication characters are detected by the secondjudging means described above, and they are judged to be the secondgeneration of the specific document, so that the copying operation isprohibited. Specifically, when the specific color code signal sent fromthe color separation table 231B composing the second judging means, is"1" it is judged that the document is of the second generation copy ofthe specific document.

Concerning the method for judging the specific document of the firstgeneration, the following two methods may be adopted:

One is a method shown in another example of the present invention, inwhich the specific document is recognized using a sheet of paper, thebackground color of which is specific. The other method is shown inFIGS. 17(A) and 17(B) , in which the specific document is recognized bythe existence of a specific mark. In the method in which the specificdocument is recognized by the specific mark, in the case of a colorimage reproducing apparatus, the second generation copy including thespecific mark can be made irrespective of the color of the specificmark. Accordingly, in this case, the second generation copy can berecognized by the row of characters as described above, however, whenthe color of the specific mark is changed, the second generation copycan be recognized.

For example, in the case of an original of the specific document onwhich the specific mark is recorded as a red stamp as illustrated inFIG. 17(A), color processing is executed, and the specific mark ischanged into a color slightly different from the original red, such aspurple red, or a color completely different from the original red, suchas blue, as illustrated in FIG. 17(B). In this way, the color, changedinto a different color, is recorded on the second generation copy. Inthis case, it is not necessary to write a row of indication charactersexpressing the second generation copy, and only the first judging meansis used for discriminating between the original of the specific documentand the second generation copy. Therefore, it is possible to omit thesecond judging means.

In the case where the original of the specific document and the secondgeneration copy are discriminated by the background color and the row ofindication characters, the first judging means discriminates thebackground color, and the second judging means discriminates the row ofindication characters. Concerning the discriminating method between theoriginal and the second generation copy, two sets of combinations areprovided. One is a case in which the background color is used for thediscrimination of the original, and the row of indication characters areused for the discrimination of the second generation copy. The other isa case in which the row of indication characters are used for thediscrimination of the original, and the background color is used for thediscrimination of the second generation copy.

The specific construction will be explained as follows.

In FIG. 14, the document OG is placed on the platen glass PG. Lightreflected by the document OG is projected to the dichroic mirror DMcomposing the optical image reading system. Then the light is subjectedto spectral processing by the dichroic mirror so as to be separated tored and cyan images. After that, the images are respectively formed onthe line sensors LS1 and LS2. In this case, the cutoff wave length ofthe dichroic mirror DM is about 540 nm. Due to the foregoing, the redcomponent is transmitted and the cyan component is reflected. The linesensors LS1 and LS2 respectively output currents I_(R) and I_(C) inaccordance with the light intensity. These line sensors LS1 and LS2 areincluded in the image reading section AA. These currents I_(R) and I_(C)are subjected to shading-compensation by the A/D converters AD1 and AD2.At the same time, these currents I_(R) and I_(C) are A/D-converted intodigital image signals V_(r) and V_(c) of 6 bits, and sent to the colorseparation tables 231A, 231B. The digital signal V_(r) shows a densitylevel of the red component, and the digital signal V_(c) shows a densitylevel of the cyan component of the document image.

A high speed ROM is used for the color separation tables 231A, 231B, andpredetermined data is previously written in the color separation table231 as shown in FIG. 13. Specifically, 8 bit data is written in thecolor separation table, wherein the 8 bit data relates to the recordingcolor corresponding to the 6 bit digital image signal V_(r) showing thedensity level of the red component, and also corresponding to the 6 bitdigital image signal V_(c) showing the density level of the cyancomponent. In this case, the data relating to the recording colorcomposing the color separation tables 231A, 23B is, for example, the 3bit color code data for designating the color of developer, and the 5bit density data for determining the density of the recording color.Consequently, the color separation tables 231A, 231B output the datarelating to the recording color in the form of a color signal.

Since the color separation tables 231A, 231B are constructed in themanner described above, a color signal of 8 bits can be outputted,wherein the color signal is composed of color code and density data ofthe recording color corresponding to the digital image signals V_(r) andV_(c).

The reason why the color separation tables 231A and 231B are separatelyprovided is related to the number of bits composing a color signal. Asdescribed in FIG. 13, the specific color region in this example isdetermined by the color and density. Consequently, in the case where aplurality of specific color regions are provided in the same colorregion in the color separation map shown in FIG. 13, the bit number ofspecific color codes described later must be increased. However, in thisexample, it is impossible to provide the specific color code, the bitnumber of which is not less than one. In this example, a plurality ofspecific color regions are provided in the same color region in thecolor separation map. Therefore, in order to discriminate the specificcolor regions, the color separation tables 231A and 231B are separatelyprovided. In this connection, if the bit number of the specific colorcode can be increased, of course, a single color separation table can beadopted. When the specific color code is made to be a signal independentfrom the color signal, the single color separation table can be adoptedfor the construction.

The color codes are determined by the specification. For example, thecolor codes are shown on Table 4.

According to the color separation map shown in FIG. 13, the first andsecond specific color regions are provided in the red region. Therefore,the color code is "110". However, the present invention is not limitedto the specific example, and the specific region can be set in eitherregion in the color separation map shown in FIG. 13. Further, aplurality of regions can be set by the setting means 232 shown in FIG.9.

The density data can be expressed by the following expression.

    (Density Data)=(V.sub.r +V.sub.C)/2

As expressed above, the density data is obtained when the density levelof the cyan component and that of the red component are averaged.

Since the color separation tables 231A and 231B are constructed in themanner described above, a color signal of 8 bits can be outputted,wherein the color signal is composed of color code and density data ofthe recording color corresponding to the digital image signals V_(r) andV_(c).

Specifically, the color separation tables 231A and 231B are exclusivelyused for pre-scanning. In this example, a color separation tableexclusively used for the image formation process is separately provided,which will not be described here.

In this example, the image processing section BB includes A/D convertersAD1, AD2 and color separation tables 231A, 231B.

The control section 230 compares a color code signal of 3 bits sent outfrom the color separation table 231A, with the first setting color codedata "110" corresponding to the background color of the specificdocument, wherein the first setting color code data "110" is previouslyset. In the case of the construction in which the original isdiscriminated by the background color, it is discriminated that thedocument OG to be copied is the original of the specific document. Inthe case of the construction in which the second generation copy isdiscriminated by the background color, it is discriminated that thedocument OG is the second generation copy of the specific document.

The control section 230 compares a color code signal of 3 bits sent outfrom the color separation table 231B, with the first setting color codedata "110" corresponding to the row of indication characters of thespecific document, wherein the first setting color code data "110" ispreviously set. In the case of the construction in which the original isdiscriminated by the row of indication characters, it is discriminatedthat the document OG to be copied is the original of the specificdocument. In the case of the construction in which the second generationcopy is discriminated by the row of indication characters, it isdiscriminated that the document OG is the second generation copy of thespecific document.

In this case, the first specific document prohibition mode operates asfollows. In accordance with the color code signal "110" sent out fromthe color separation table 231A, the image formation process followingthe pre-scanning operation is stopped in the mode. That is, the controlsection 230 determines whether the image forming process following thepre-scanning operation is continued or not, wherein the determination isconducted by the existence of a release signal obtained when the releaseswitch on the operation panel 210 is pressed.

The control section 230 judges whether the specific document of thegeneration is to be copied or not, by the existence of the releasesignal. On the other hand, even when the control section 230 hasreceived a release signal, a display of "warning" is made on the displaypanel provided on the operation panel 210. Sometimes, instead of thedisplay of "warning", a display is made which shows that the specificdocument is subjected to the generation copying operation. Consequently,the control section 230 corresponds to the warning and prohibitionmeans.

In the case where the original of the specific document is to be copied,the control section 230 receives the withdrawal of prohibition ofcopying operation by means such as a control key or ID card shown inanother example, and when the withdrawal switch provided on theoperation panel 210 is pressed so as to receive the withdrawal signal,the prohibition of copying operation can be withdrawn. However, in thecase where the second generation copy of the specific document is to becopied, the withdrawal of prohibition of copying operation conducted bymeans such as the control key or ID card, is not received.

In the case where the original of the specific document is copied, therow of indication characters expressing the second generation arewritten in addition to the document image to be copied on a sheet ofrecording paper, by a developing unit such as a developing unit 222Y,222M or 222C which is not a black developing unit. Due to the foregoing,in the case where the second generation is further copied, thewithdrawal of prohibition of copying operation is not received. Whenthis technique is applied, the generation copy can be prohibited notonly at the second generation but also at any designated generation.

The control section 230 is provided with a function for storing acharacter composing the specific mark attached to the specific document,wherein the character is stored in the manner of a halftone dot. By thisfunction, dot data is stored so that the specific mark read by the imagereading section AA or the specific mark previously registered isreproduced in the manner of a rough halftone dot.

By the information of the specific mark stored in this memory, thecontrol section 200 recognizes the specific mark. Therefore, thisrecognition system is used for an embodiment in which the specificdocument is recognized by the existence of the specific mark.

The operation panel 210 is provided with a liquid crystal display fordisplaying a warning sign, and also provided with a release switch forreleasing the prohibition condition of image forming operation. Theoperation panel 210 corresponds to the release means, and a modeselection switch is provided for selecting between the first and secondspecific document prohibition modes.

When a signal is inputted into the control section 230 from theoperation panel 210, the control section 230 controls the image readingsection AA, image processing section BB, writing section CC, imageforming process section DD, and sheet supply system EE, so that theimage forming process can be carried out.

With reference to FIG. 7 and FIGS. 13 to 15, the pre-scanning operationconducted in the image reproducing apparatus 200 of this example will beexplained as follows.

First, the pre-scanning operation in the first specific documentprohibition mode will be described.

First, the operator opens the platen cover PK and puts the document OGon the platen glass PG. Then the operator sets the number of copiesusing the operation panel 210, and presses the copy switch withoutpressing the release switch. As illustrated in FIG. 15, the controlsection 230 turns on the light source 202. Then the light source 202 ismoved at a predetermined speed while the light source 202 illuminatesthe surface of the document OG with white light, the illuminated portionbeing formed rectangular. The control section 230 moves the V mirrorsection M22 at half the speed of the light source 202 in the samedirection as that of the light source 202. Due to the foregoing, thedocument OG is scanned. A beam of light reflected on the surface of thedocument OG is reflected by the first, second and third mirrors 203,204, 205. Then the beam of light is divided into a red and a cyancomponent by the action of the dichroic mirror DM. Then a red image isformed on the red line sensor LS1 by the image formation lens 206, and acyan image is formed on the cyan line sensor LS2. The scanning conductedby the image reading section AA is the pre-scanning conducted before theimage formation process.

Electric currents I_(R) and I_(C) outputted from the red and cyan linesensors LS1 and LS2 in the pre-scanning, are respectively subjected toshading compensation by the A/D converters AD1 and AD2. At the sametime, the currents are subjected to the A/D conversion, so that thecurrents are converted into the digital image signals V_(r) and V_(C) of6 bits, and then the image signals are sent to the color separationtables 231A and 231B. The color separation tables 231A and 231B send acolor signal of 8 bits corresponding to the digital image signal to thecontrol section 230.

The control section 230 compares a color code signal of 3 bits sent outfrom the color separation table 231A, with the first setting color codedata "110" corresponding to the background color of the specificdocument, wherein the first setting color code data "110" is previouslyset. In the case of the construction in which the original isdiscriminated by the background color, it is discriminated that thedocument OG to be copied is the original of the specific document. Inthe case of the construction in which the second generation copy isdiscriminated by the background color, it is discriminated that thedocument OG is the second generation copy of the specific document.

The control section 230 compares a color code signal of 3 bits sent outfrom the color separation table 231B, with the first setting color codedata "110" corresponding to the row of indication characters of thespecific document, wherein the first setting color code data "110" ispreviously set. In the case of the construction in which the original isdiscriminated by the row of indication characters, it is discriminatedthat the document OG to be copied is the original of the specificdocument. In the case of the construction in which the second generationcopy is discriminated by the row of indication characters, it isdiscriminated that the document OG is the second generation copy of thespecific document.

In the case where the color code signals sent from the color separationtables 231A, 231B do not coincide with the first and second specificcolor codes, the control section 230 continues the image forming processfollowing the pre-scanning operation. In the case where only the colorcode signal sent from the color separation table 231A coincides with thefirst specific color code as a result of the comparison, since thecontrol section 230 does not receive a release signal as describedbefore, in accordance with the programing in the first specific documentprohibition mode, a display such as "Prohibition of a ConfidentialDocument". "Prohibition of Unapproved Copying Operation", "Prohibitionof Enterprise Confidential", or "Prohibition of Business Confidential"is made on the liquid crystal display on the operation panel 210, sothat the operator can be given a caution, and the following imageforming process is not carried out. Further, even when a copying commandsignal is continuously given by the operation panel 210, the imageforming operation is not carried out. Due to the foregoing, the copyingoperation of the specific document can be prohibited. In the case whereonly the color code signal sent from the color separation table 231Bcoincides with the second specific color code as a result of thecomparison, since the control section 230 does not receive a releasesignal as described before, in accordance with the programing in thefirst specific document prohibition mode, a display, such as"Confidential", "Unapproved Copy", "Enterprise Confidential" or"Business Confidential", is made on the liquid crystal display on theoperation panel 210, so that the operator can be given a caution, andthe following image forming process is not carried out. Due to theforegoing, the copying operation of the specific document of the secondgeneration and after that can be prohibited. The operation of the firstspecific document prohibition mode is described above. According to thefirst specific document prohibition mode, not only the copying operationof the specific document but also the generation copying operation isprohibited.

Next, the operation in the second specific document prohibition modewill be described as follows.

When the release switch is pressed, a release signal is sent. When thecontrol section 230 received this release signal from the operationpanel 210, the operation in the second specific document prohibitionmode is carried out. Although the color code of 3 bits sent out from thecolor separation table 231A has coincided with the first specific colorcode data "110" corresponding to the background color of the specificdocument, a display, such as "Confidential", "Unapproved Copy","Enterprise Confidential", or "Business Confidential", is made on thedisplay of the operation panel 210. Therefore, only attention is causedto the operator, and the specific image forming processing is continued.At this time, the color code data of 3 bits sent out from the colorseparation table 231B does not coincide with the second specific colorcode data "110" that has been previously set, because the controlsection 230 recognizes not only the color code signal but also thecoincidence of the density signal.

In accordance with the KNC (Konica New Process), the specific imageforming process will be explained, wherein the KNC is an image formingprocess in which a plurality of layers of toner images are formed on theimage forming body 220.

In order to erase the image hysteresis, the image forming body 220 isdischarged when exposure is conducted by the PCL in which a lightemitting diode is used. Then the circumferential surface of the imageforming body 220 is given a uniform electric charge of VH (-600 to -800V) by the scorotron charger 221 having a grid and discharging wire, theelectric potential of which is maintained at VG (-550 to -850 V).

The writing section CC forms a latent image in the primary scanningdirection when a laser beam is irradiated on the image forming body 220in accordance with a color signal. By the effect of the rotation of theimage forming body 220, a latent image is also formed in the subsidiaryscanning direction. In this way, a latent image can be formed on thecircumferential surface of the image forming body 220 when imageexposure is conducted in both the primary and subsidiary scanningdirection. In this example, exposure is conducted on a characterportion, so that the electric potential of the character portion becomeslow, that is, the electric potential of the character portion becomesV_(L) (-100 to 0 V). In this way, what is called a reversal latent imageis formed.

Around the circumference of the image forming body 220, the developingunits 222Y, 222M, 222C and 222BK are disposed, in which developerscontaining yellow, magenta, cyan and black toners and carrier areaccommodated.

Each of the developing units 222Y, 222M, 222C and 222BK includes adeveloping sleeve in which a magnet is accommodated, and developer isheld on the developing sleeve by the action of electrostatic force andconveyed to the developing region. At this time, the layer thickness ofdeveloper is regulated by a layer forming rod, so that the layerthickness is 300 to 600 μm on the developing sleeve. The developerincludes carrier and toner, wherein a carrier particle is composed of acore made of ferrite and the core is coated with insulating resin, and atoner particle is made of pigment of polyester, electric chargecontrolling agent, silica and titanium oxide.

A gap between the developing sleeve and the image forming body 220 inthe developing region is larger than the layer thickness of developer,that is, the gap is 0.4 to 1.0 mm. An AC bias of V_(AC) (1.5 to 3.0KV_(p-p)) and a DC bias of V_(DC) (-500 to -700 V) are superimposed andimpressed in the gap. Since the polarity of V_(DC) and V_(H) and that oftoner are the same, the toner particles are released from the carrierparticles, and they are not deposited on a portion of electric potentialV_(H) which is higher than V_(DC), but they are deposited on a portionof electric potential V_(L) which is lower than V_(DC). In this way, thelatent image can be made visual. This development is reversaldevelopment. In this way, visualization of the first color is completed.

The specific image forming process will be described as follows. In theimage exposing process conducted by the writing section CC, a hatchedportion is formed in the background by at least one of the developingunits 222Y, 222M, 222C. Alternatively, the background is reproduced by athin intermediate color belonging to the second specific region in thecolor separation map shown in FIG. 13. Further, the above methods arejointly used. Furthermore, the specific mark may be formed in the mannerof a rough halftone dot.

In the image forming process of the second color, the image forming bodyis uniformly charged by the scorotron charger 221, and a latent image ofthe second color is formed by the writing section CC in accordance withthe image data of the second color. Due to the foregoing, a latent imageof the document and that of the background including a hatched portionare formed. In this case, the discharging operation that has beenconducted in the first color image forming process is not performed inorder to prevent the toner particles deposited on the first color imageportion from scattering due to a sharp decrease in the electricpotential.

While the photosensitive layer on the image forming body 220, theelectric potential of which is V_(H), the same latent image as that ofthe first color is formed in a portion where the first color image hasnot been formed. In a portion where the first color image has alreadybeen formed , a latent image of V_(M) is formed by the light shieldingeffect of the deposited toner of the first color and the electric chargeof toner itself. Therefore, development is performed in accordance withthe potential difference between V_(M) and V_(DC). In order to keep thebalance between the first and second colors, an amount of exposure ofthe first color is reduced, so that an intermediate electric potentialsatisfying the following inequality is maintained.

    V.sub.H >V.sub.M (-100 to -300)>V.sub.L

With respect to the third and fourth colors, the same image formingprocess as that of the second color is conducted, and a visual image of4 colors can be formed on the circumferential surface of the imageforming body 220.

As described above, according to the image reproducing apparatus 200 ofthis example, the first generation copy of the specific document isallowed. However, due to the aforementioned KNC process, the secondgeneration copy of the specific document is provided with a hatchedportion of an intermediate color on its background, or a reproducedcolor of the specific mark expressing the specific document isdifferent, and further the specific mark is reproduced in the manner ofa halftone dot. Therefore, the second generation copy and after that canbe easily discriminated from the first generation copy that is theoriginal.

When the release switch is pressed, a release signal is sent. When thecontrol section 230 received this release signal from the operationpanel 210, the operation in the second specific document prohibitionmode is carried out. In the case where the color code of 3 bits sent outfrom the color separation table 231B has coincided with thepredetermined second specific color code data "110", a display of"Confidential" or "Illegal copy" is made on the display of the operationpanel 210, so that attention is caused to the operator, and not only thespecific image forming processing following the pre-scanning operationbut also the normal image forming process is not conducted. As describedabove, in the second specific document prohibition mode, the secondgeneration copying operation and after that can be prohibited.

An example of the digital image reproducing apparatus is explainedabove, in which the original of the specific document and the secondgeneration copy are discriminated. Even in the analog image reproducingapparatus, the original of the specific document and the secondgeneration copy can be discriminated.

Since the analog image reproducing apparatus is excellent indiscriminating the overall background color, recording sheets ofdifferent background colors may be used for the specific document andthe second generation copy, and these different background colors may bepreviously registered. As shown in FIG. 18, when a color correspondingto a hatched portion in the red region and a color corresponding to ahatched portion in the blue region are used for the background colors ofthe specific document and the second generation copy, it is possible todiscriminate between the original of the specific document and thesecond generation copy. Of course, any combinations of colors may beadopted for the background colors. The color combination may beappropriately determined in accordance with the accuracy of the judgingmeans.

Since the image reproducing apparatus 200 of this example is constructedas explained above, the first generation copying operation of thespecific document can be allowed, however, the second generation copyingoperation and after that can be prevented.

What is claimed is:
 1. An image forming apparatus with an unapprovedcopy preventor, comprising:a document support for supporting an originaldocument, said original document comprising data provided on a sheet ofmaterial formed of a single material, said sheet of material having abackground color, said background color having predetermined wavelengthcomponents; an irradiator for irradiating said original document with anirradiating light beam; a detector for detecting the predeterminedwavelength components in a reflected light reflected from said originaldocument which is irradiated with said irradiating light beam; saiddetector generating detection signals based on a detection of saidpredetermined wavelength components in said reflected light; and anevaluation circuit for determining whether said original document is adocument which prohibits a production of an unapproved copy thereofbased on said detection signals.
 2. The image forming apparatus of claim1, wherein said irradiator irradiates said original document with saidirradiating light beam for a predetermined period of time after a lightsource of said irradiator is turned on, and said light beamsubstantially comprises said predetermined wavelength components.
 3. Theimage forming apparatus of claim 1, further comprising:a display fordisplaying that a reproduction of the original document is prohibitedwhen said evaluation circuit determines that said original document issaid document which prohibits production of an unapproved copy; and acontroller for preventing a copying operation of said image formingapparatus when said evaluation circuit determines that said originaldocument is said document which prohibits production of an unapprovedcopy thereof.
 4. An image forming apparatus with an unapproved copypreventor, comprising:a document support for supporting an originaldocument, said original document comprising data provided on a sheet ofmaterial formed of a single material, said sheet material having abackground color, said background color having predetermined wavelengthcomponents; an irradiator for irradiating said original document with anirradiating light beam; a detector for detecting a reflected light fromsaid original document which is irradiated with said irradiating lightbeam; said detector generating detection signals based on a detection ofsaid reflected light; a converter for converting said detection signalsto digital image signals which include data regarding said backgroundcolor; a color separator coupled to receive said digital image signalsfrom the converter for determining from said digital input signals saidbackground color of said sheet of material and a density of said digitalimage signals, said color separator generating color signalscorresponding to said background color and said density of said digitalimage signals; and an evaluation circuit for determining whether saidoriginal document is a document which prohibits a production of anunapproved copy thereof based on said color signals.
 5. The imageforming apparatus of claim 4, wherein:said color separator includes acolor map, with which a color in said digital image signals isdetermined; and said color map includes a specific color region, whichcorresponds to the background color of said original document; and saidimage forming apparatus, further comprises a setting device for settinga location of said specific color region in said color map.
 6. The imageforming apparatus of claim 5, wherein said setting device sets saidlocation of said specific color region in said color map by readingcolor data of said background color of said original document with saiddetector.
 7. The image forming apparatus of claim 5, furthercomprising:a security controller for preventing said setting device fromsetting said location of said specific color region in said color mapuntil at least one of a control key, an ID card and a code number isprovided by said security controller.
 8. The image forming apparatus ofclaim 6, further comprising:a counter for counting a frequency of saiddigital image signals at a respective density level; a color ghostdetector for detecting color ghost data, mapped in a color area, excepta black color area, in said color map, of said digital image signals,said color ghost detector counting a sampling number of said color ghostdata; and a subtractor for subtracting said sampling number of saidcolor ghost data from said frequency of said digital image signals atthe respective density level so as to obtain an effective color data;wherein said evaluation circuit determines whether said originaldocument is said document which prohibits a production of an unapprovedcopy thereof based on said effective color data.
 9. The image formingapparatus of claim 6, wherein said setting device sets a size of saidspecific color region by providing a predetermined enhancement based onsaid color data of said background color of said original document withsaid detector.
 10. An image forming apparatus with an unapproved copypreventing means, comprising:a document supporting means for supportingan original document; an irradiating means for irradiating said originaldocument with a light beam; a detecting means for detecting a reflectionlight from said original document which is irradiated with said lightbeam; said detecting means for generating detection signals according tothe detection of said reflection light; a converting means forconverting said detection signals to digital image signals; a colorseparating means for determining a color and a density of said digitalimage signals; said color separating means for generating color signalscorresponding to said color and said density of said digital imagesignals; wherein said color separating means includes a color map withwhich a color of said digital image signals is determined; and aspecific color region, which corresponds to a color of a specific markon said original document, is provided in said color map; a firstcounting means for counting a number of said digital image signalscorresponding to said specific mark; a second counting means forcounting a overall number of said digital image signals corresponding tosaid color of said specific color region; and a judging means fordetermining whether said original document is a document which prohibitsan unapproved copy by comparing said number of said digital imagesignals corresponding to said specific mark with said overall number ofsaid digital image signals corresponding to said color of said specificcolor region.
 11. The image forming apparatus of claim 10, wherein saidfirst counting means counts said number of said digital image signalscorresponding to said specific mark without outer frame of said specificmark.
 12. The image forming apparatus of claim 10, wherein said firstcounting means counts said number of said digital image signalscorresponding to said specific mark with outer frame of said specificmark.
 13. The image forming apparatus of claim 10, further comprising:ablurred image detecting means for detecting a blurred portion of saidspecific mark on said original document; said blurred image detectingmeans for generating blurred portion signals; and a blurred imagecompensation means for compensating said digital image signalscorresponding to a blur of said specific mark according to said blurredportion signals.